lable at ScienceDirect

Journal of Natural Gas Science and Engineering 46 (2017) 119e131

Contents lists avai

Journal of Natural Gas Science and Engineering

journal homepage: www.elsevier .com/locate/ jngse

Effective evaluation of gas migration in deep and ultra-deep tightsandstone reservoirs of Keshen structural belt, Kuqa depression

Yunqi Shen a, b, Xiuxiang Lü a, b, *, Song Guo a, b, Xu Song a, b, Jing Zhao c

a College of Geosciences, China University of Petroleum, Beijing 102249, Chinab State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, Chinac Faculty of Engineering, University of Regina, Regina, SK S4S 0A2, Canada

a r t i c l e i n f o

Article history:Received 22 November 2016Received in revised form17 April 2017Accepted 23 June 2017Available online 2 August 2017

Keywords:Kuqa depressionKeshen structural beltGas migrationFluid potentialGas source fault

* Corresponding author. College of Geosciences, ChBeijing 102249, China.

E-mail addresses: 675979924@qq.com (Y. Shen86270220@qq.com (S. Guo), 396075562@qq.com (X(J. Zhao).

http://dx.doi.org/10.1016/j.jngse.2017.06.0331875-5100/© 2017 Elsevier B.V. All rights reserved.

a b s t r a c t

The gas reservoir in the Keshen structural belt, Kuqa depression, Tarim Basin, Xinjiang, China is a typicaldeep and ultra-deep structural faulted anticline tight sandstone gas reservoir. This reservoir possessesabundant natural gas and exhibits a promising exploration and development prospective. However, theeffectiveness of the gas migration (preferred migration pathway) and the contribution of gas sourcefaults as a dominant migration pathway remains to be further investigated. Therefore, this paper ex-amines gas-source correlation to determine the source of natural gas and uses fluid potential analysiscombined with the tracer results of geochemical parameters to predict the predominant migration andaccumulation pathways of natural gas. Next, the paper determines the contribution of gas source faults tothe formation of the gas reservoir during the migration process by making a quantitative assessment ofthe gas source faults. The results show that the predominant source of natural gas from the deep andultra-deep tight sandstone gas reservoir in the Keshen structural belt, Kuqa depression is Jurassic andTriassic source rock. Structural units with relatively low fluid potential represent the predominantmigration pathway of natural gas. Gas source faults provide the predominant natural gas verticaltransport pathway, with differences observed between zones in the south and north. The greater thecontribution provided by a gas source fault during transport is, the higher the accumulation that results.The effectiveness of the natural gas migration deep and ultra-deep tight sandstone gas reservoir in theKeshen structural belt, Kuqa depression is as follows: Kela2 trap > Keshen6 trap > Keshen8trap > Keshen2 trap > Keshen13 trap > Keshen9 trap. This method can be used in effective evaluation ofthe gas migration under the similar tectonic settings and reservoir formation conditions.

© 2017 Elsevier B.V. All rights reserved.

1. Introduction

Hydrocarbon migration is an important aspect of hydrocarbonsystems, being the link between all aspects of the process of hy-drocarbon generation, expulsion, migration, accumulation and loss(Magoon and Dow,1994; Losh et al., 1999; Aydin, 2000). However, itis one of the major challenges in the petroleum research because ofthe lack of direct geological evidence and the extreme conditionsrequired for the experimental physical simulation of hydrocarbonmigration (Pang et al., 2013; Chen et al., 2014). For deep and ultra-

ina University of Petroleum,

), luxx@cup.edu.cn (X. Lü),. Song), 983921671@qq.com

deep layer tight sandstone gas reservoirs, the contributions to theeffectiveness of gas migration, including the predominant directionof migration and path of migration in a gas source fault, on such gasreservoir accumulation is an intriguing research topic.

Varying geothermal gradients and explorations of target layershave resulted in different understandings and definitions of deeplayers. The threshold depth of a deep layer is defined as 4500 m bythe US and Brazil, 5000 m by Total S.A., and 4000 m by Russia. Foroil and gas exploration in China, the definition of a deep layer dif-fers between the eastern and western regions. In the western re-gion, an embedded depth from 4500 m to 6000 m is defined as adeep layer, and a burial depth exceeding 6000 m is defined as anultra-deep layer. In the eastern region, a burial depth from 3500 mto 4500 m is defined as a deep layer, and an embedded depthexceeding 4500 m is defined as an ultra-deep layer. Regular drillingengineering in China defines a drilling depth from 4500 m to

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131120

6000m as a deep layer and a drilling depth exceeding 6000m as anultra-deep layer (Ma et al., 2011; Zhang et al., 2015).

Many scholars throughout the world have defined a tightsandstone reservoir as one with permeability less than 0.1 mD.(Elkins, 1978; Macavoy, 1979; Spencer, 1983; Li et al., 2012a).Because this study area is in the Tarim Basin of China, according tothe trade standard of tight sandstone gas engineering in China (SY/T 6832e2011), a tight sandstone reservoir has a porosity less than10% and permeability less than 0.1 mD. There are different classi-fication criteria and methods for a tight sandstone reservoir thathave been proposed in previous studies. According to the relation insequence between the charging of the hydrocarbon and compact-ing of the formation, a tight sandstone gas reservoir is categorizedinto two circumstances: compaction after charging and chargingafter compaction (Davis, 2011). According to its characteristics, atight sandstone gas reservoir can be categorized into good (tight),medium (extra-tight) or bad (ultra-tight) cases (Guan et al., 1995).According to the characteristics of a tight sandstone gas reservoir,including the storage and height of the structural position, it can becategorized as a continuous tight sandstone gas reservoir or trap-ped tight sandstone gas reservoir (Dai et al., 2012). According to themode of accumulation, a tight sandstone gas reservoir is catego-rized into continuous gas accumulation zones and transition zones(Schmoker, 2002). According to its tectonic position in the basin, atight sandstone gas reservoir is categorized as slope type, archedstructure type or deep depression type (Li et al., 2012b).

The major gas reservoir of the Cretaceous Bashijiqike formationis buried deeper than 5000 m in the Keshen structural belt, Kuqadepression, with a 2%e6% matrix porosity and 0.01e0.1 mDpermeability, making it a typical tight gas reservoir with deep andultra-deep faulted anticlines. There have been many studies ofvertical migration though faults (Philippi, 1965; Hooper, 1991).According to previous research, there is a series of thrust faultsdeveloped in the pre-salt deep layer of the Keshen structural belt,Kuqa depression, which connects deep hydrocarbon source rockand provides the main path for oil and gas migration vertically(Wang, 2014). However, the contributions to the effectiveness ofthe gas migration, including the predominant direction and path ofmigration in a gas source fault, on such types of gas reservoiraccumulation have not been studied systematically. Therefore, thisresearch provides an evaluation of the effectiveness of gas migra-tion in the target area.

2. Geological setting

The Kuqa depression is a transition region between the SouthTianshan Mountain orogenic belt, which is located on the northern

Fig. 1. Regional tectonic locations of the Kuqa de

part of the west Tarim Basin, China. This belt is west of the Wushidepression, east of the Yangxia depression, south of the Tianshan,and north of the Tabei uplift. The majority of the land surface iscomposed of hilly areas and gobi. The length from east to thewest is500 km, and the width from south to north is approximately30e70 km with an exploration area of 2.8*104 km2. From the laterstage of the Neogene, the Kuqa depression can be divided into fiveparts from north to south: the northern monoclinic structure zone,the Kelasu-Yiqikelike fold-thrust zone, the Wushi-Baicheng-Yangxia depression, the Qiulitak tucker anticlinal structural zoneand the Northern Tarim uplift belt (Wang et al., 2016; Liang et al.,2003; Jia and Li, 2008) (Fig. 1). The Keshen structural belt is onthe Keshen segment of the Kelasu structural zone, Kuqa depression,Tarim Basin (Fig. 2). The northern part of the gas reservoir surface isa hilly area with a general altitude above 1800 m. A quaternaryalluvial fan is developed on the south, with an approximate altitudeabove 1400 me1500 m and a slope of 2e3. The Klasu river passesthrough the western part of the gas reservoir, generating acomplicated surface structure.

2.1. Structural characteristics

The Keshen structural belt has mainly developed north thrustfaults. According to the fault scales, breaking strata, the Keshendistrict can be divided into three levels: the primary faults controlthe tectonic distribution characteristics of the whole Keshenstructure belt; the secondary faults control the distribution of theanticlines; and the tertiary faults are the internal fractures of thefault blocks. Two primary faults are developed on the Keshenstructural belt: the Kelasu fault on the northern border and theBaicheng fault on the southern border. These two faults control thestructural distribution characteristics of the Keshen structural belt.Between those two boundaries, five secondary faults (F1, F2, F3, F4,and F5) are developed that segment the Keshen structural belt into6 secondary fault blocks, along with the Kela2 fault block on thenorthern part of the Crassus fault; these blocks are segmented byseveral tertiary faults, complicating the structure further (Fig. 3).

2.2. Stratigraphic characteristics

The stratigraphic sequence of the Keshen structural belt isdivided into the following parts from top to bottom: Quaternary(Q),Neogene Kuqa formation(N2k), Kangcun formation(N1-2k), Jidikeformation(N1j), Palaeogene Suweiyi formation(E2-3s), Kumuge-liemu group(E1-2km); Mesozoic Cretaceous Bashijiqike for-mation(K1bs), Baxigai formation(K1bx), Shushanhe formation(K1s),Yagelimu formation(K1y); Jurassic Kelazha formation(J3k), Qigu

pression in the Tarim Basin, western China.

Fig. 2. Belt differentiation map of the Kelasu structural belt of the Kuqa depression in the Tarim Basin, western China.

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131 121

formation(J3q), Qiakemak formation(J2q), Kezinur formation(J2kz),Yangxia formation(J1y), Ahe formation(J1a); Triassic Taliqik for-mation(T3t), Huangshanjie formation(T3h), Karamay for-mation(T2k), and Ehuobulak formation(T1e) (Fig. 4).

Among these parts, swamp facies and lacustrine facies sourcerock are developed in the Triassic-Jurassic Kuqa depression,including hydrocarbon source rocks in the Triassic Taliqik for-mation(T3t) and the Early Jurassic Kezinur formation(J2kz) andlacustrine source rocks in the Yangxia formation(J1y), the Middle-upper Triassic Karamay (T2k) and Huangshanjie (T3h) formationsand the middle Jurassic Chuck mark formation(J2q). Except for thelacustrine source rocks developed in the Qakemak formation(J2q),which are of sapropelic type, the source rocks developed in theHuangshanjie formation(3h) and the Karamay formation(T2k) aremainly the humus type (Zhao et al., 2005; Qin and Dai, 2006;Wang,2014).

The Cretaceous Bashijiqike formation is the principal gas-bearing interval. The depth of the Cretaceous Bashijiqike

Fig. 3. Typical faults on the NS-trending seismi

formation within the Keshen structural belt is 210 me350 m. Aclear three-section characteristic can be seen with slight depthchanges, and it can be divided into three layers from top tobottom.

The first lithological unit (K1bs1): The remaining depth of the

Keshen structural belt is 47 me70.5 m with an average depth of51.1 m, because of erosion. This unit is mainly composed of brownto dark brown medium-huge thickness sandstone, with thin-medium thickness mudstone in parts. With comparatively roughgranularity, the sandstone in this unit is mainly medium-finegrained, with mud-gravel sandstone at some locales.

The second lithological unit (K1bs2): The depth of the second

unit in the Bashijiqike formation is 93e196.5 m. The lithologicalcharacteristics are dark brown thick to super-thick mudstone, siltymudstone and siltstone. The particle size is similar to that in thefirst unit and is primarily characteristic of middle-fine sandstoneand medium sand embedded with thick medium sand and silty-fine sand. Additionally, sandstone often consists of boulder clays

c profile across the Keshen structural belt.

Fig. 4. Stratigraphic column of the Keshen structural belt in the Tarim Basin, western China.

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131122

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131 123

that are accumulated locally. A higher natural gamma and a largernumber of mudstone interlayers compared with the first unitindicate the relative purity of this unit.

The third lithological unit (K1bs3): The depth is approximately

70e83 m, with an average depth of 74.25 m. This lithologicalmember has an abundance of medium to thick layers of finesandstone with thin layers of mudstone and silty mudstone. Theupper lithology is characterized by medium layers of fine sand-stone and silty mudstone, and developments of thin-layermudstone are frequent. The lower lithology is mainly character-ized by thick-layer bulk fine sandstone interbedded with siltymudstone and mudstone with small interlayers and small mono-layer thickness.

The distribution of the Kumugeliemu group (E1-2km) thick-layergypsum salt rock in the Kuche depression and Kuche structural beltis stable, constituting the Cretaceous Bashijiqike formation (K1bs)sandstone large-scale gas field fine regional cap formation (Tanget al., 2007; Zhuo et al., 2013, 2014), and providing an effectivebarrier to the per-salt overpressure gas reservoir (Lu et al., 2007).

3. Data and methods

The seismic data for the Keshen structural belt, Kuqa depression,Tarim Basin was collected by a 3D exploration during 2008e2009.This exploration was conducted in 120-folds with an anterior full-coverage area of 1002.1 km2 and an acquisition binning of15m*30m. Themain determined gas reservoirs are Kela2, Keshen6,Keshen2, Keshen8, Keshen9, and Keshen13. Thirty typical through-well seismic sections were selected, transformed into the depthdomain, and used to conduct statistical and analytical calculationsto interpret the fault displacement, fault dip and extended distanceof the fault strike and the vertical distance between the top of thereservoirs and source rocks that were connected by a fault. In thisstudy, 20 wells were selected from the exploration wells in thestudy zone; these were used primarily to conduct statistical anal-ysis on the natural gas geochemical parameters, reservoir tem-perature and pressure data from the Bashijiqike formation, thatprovide the information needed to study the natural gas migrationpathways.

Suitable parameter selection and the existence of multipleinfluencing factors are two of the main difficulties in the study ofnatural gas migration. Some useful parameters have already beenfound, such as carbon isotopes (Colombo et al., 1969; Schoell, 1983;Shamsuddin and Khan, 1991), carbon and hydrogen isotopes inmethane, CO2 content and its carbon isotopes, the benzene/nC6ratio, the gas aridity coefficient (Shen et al., 1991), and the iC4/nC4ratio (Fu and Liu, 1992). Because of the lack of data on both thenatural gas carbon isotopes the carbon and hydrogen isotopes inthe methane and because there were no obvious trends with thegas aridity coefficient, iC4/nC4 (iso-butane/n-butane) was selectedas the geochemical parameter used to trace the natural gasmigration pathway within the study zone.

The fluid potential analysis method is also adopted in this studyto analyse the natural gas migration pathway. A fluid tends to flowfrom higher-to lower-potential zones, no matter if it is in acompaction flow basin or in a gravity flow basin. When there is amigration pathway, oil and gas will migrate from the a high-potential zone to the surrounding low-potential zones along thepotential gradient in the negative direction (Hubbert, 1953;England et al., 1987; Liu et al., 2002). Hubbert (1953) first usedthe concept of fluid potential to describe the state of motion andbehaviour of underground fluids, and defined fluid potential as thetotal amount of mechanical energy of a fluid (potential energy,pressure energy, and water kinetic energy),

F ¼gzþ

Z p

0dp

rþ q2�2

where F is the fluid potential (m2/s2), g is the gravitational accel-eration (9.81 m/s2), z is the height of the calculating points, p is theformation pressure of calculating points (MPa), and q is the fluidflow velocity (m/s). Considering that the natural fluid movementunder underground conditions is very slow, the fluid flow velocitycan be approximated as zero.

Natural gas migration pathways can be effectively predictedby the chemical tracing technique of natural gas and fluid po-tential analysis. However, the migration amount and regulationand efficiency of natural gas accumulation are difficult todescribe briefly. Therefore, the connecting source rocks andreservoir faults, along with their ability to become migrationpathways, will be discussed in greater detail below. Verticaltransport via faults is the main transfer mechanism for the nat-ural gas generated and discharged from the source rocks tosuitable traps, causing oil and gas to accumulate. Recent studiesshow that fluid can be excited to mass migration under the ac-tion of seismic pumping during fault activity periods (Scholzet al., 1973; Sibson et al., 1975). Under the mechanism of tec-tonic pumping, deep crust fluids intrude upward along thespacious shear zone and secondary structural tension belt due tolithostatic pressure, and they accumulate along the high-permeability zone in the crust (Hayward et al., 1999). Thismigration mechanism conforms to pressure flow migration (Zhaoet al., 2000). Therefore, the extent of the fault transporting abilityis determined by the fault dimensions, the activity time duringkey hydrocarbon generation periods and the natural gasproperties.

The following parameters represent fault dimensions: (1)fault displacement (H) - A larger fault displacement is indicativeof a larger fault. Hull (1988), after conducting extensive statisticalanalyses of fault displacements and widths of fault zones, pro-posed that the two values have an obvious positive correlationdescribed by Ti ¼ 0.62Hi

0.875, i.e., the width of a fault presents apower function growth with the increase of the fault displace-ment. Therefore, based on the above analysis, the effective faultmigration space and the conductivity of fractures will increasewith fault displacement (Sun et al., 2006). (2) The width of thefault zone (T) - Natural gas will migrate vertically along a fault,and its effective migration zone is a fault network that containsmultiple accompanying fractures. With the increasing width of afault zone, the development of the fracture network inside be-comes greater and the effective migration space therefore be-comes larger. If the conditions remain constant, the amount ofnatural gas that can migrate through per unit of time is large, andthe fault conducting ability is strong. (3) Fault extension length(L) - The fault extension length is the extension area along the gassource reservoir along the trend, where a longer elongation re-flects a larger scope of the fracture network in the fault zone anda larger fault effective migration zone. If other conditions do notchange, the more natural gas that flows across the faulted regionper unit time, the better the conducting ability of the fault.Extending the length of the fault depends on the position of thetrap spill point, which means that the sampling of the extendinglength in the fault should be controlled at the trap spill point. (4)Fault height (h) and fault inclination angle (q) - For a specificfault, the vertical extending length of the fracture represents themajor path for natural gas during migration, but this is difficult todetermine. Therefore, fault height, which is defined as the ver-tical distance between the reservoir and source rock connected

Table 1Molecular compositions and dryness coefficient(C1/C1-C4) of gases from Bashijiqike formation Kuqa depression, Tarim Basin, China.

Well Strata Depth(m) Main composition (vol %) iC4/nC4 Dryness coefficient

CH4 C2H6 C3H8 iC4 nC4 CO2 N2 (C1/C1-C4)

KL203 K1bs 3698e3961 97.8250 0.7900 0.0200 0.0900 0.0550 0.7425 1.0688 1.636 0.990KS6 K1bs 5605e5653 93.1000 0.4850 0.0350 0.0037 0.0028 0.5393 0.7927 1.311 0.994KS2 K1bs 6573e6697 97.4500 0.5105 0.0445 0.0115 0.0200 0.8060 1.1400 0.575 0.994KS201 K1bs 6505e6700 97.6667 0.5817 0.0425 0.0057 0.0102 0.7472 0.8940 0.557 0.993KS203 K1bs 6600e6685 97.6700 0.5501 0.0418 0.0052 0.0100 0.8495 0.8687 0.520 0.994KS204 K1bs 6810e6830 97.0000 0.5274 0.0353 0.0049 0.0090 0.9577 1.4420 0.540 0.994KS205 K1bs 6890e6976 96.7667 0.5377 0.0363 0.0043 0.0083 1.4617 1.1537 0.520 0.994KS8 K1bs 6717e6903 97.9000 0.6470 0.0240 0.0025 0.0040 0.8120 0.5885 0.625 0.993KS9 K1bs 7445e7552 98.5000 0.3580 0.0130 0.0020 0.0050 0.6240 0.5100 0.400 0.996KS13 K1bs 7311e7430 96.9500 0.5610 0.0370 0.0040 0.0080 1.0165 1.3300 0.500 0.994

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131124

by the fault, and the fault inclination angle are introduced toestimate this value.

In addition to those four fault dimension parameters, there aretwo more parameters that are also essential to evaluate thetransport ability of the fault: (5) active time of fault during accu-mulation (t) and (6) kinematic viscosity of natural gas (m). The ki-nematic viscosity of the natural gas describes its resistance tomigration, which needs to be eliminated to evaluate the realtransport ability. This parameter is obtained from a test.

In the formation of a gas reservoir, the natural gas generatedfrom the source rock migrates upstream through the transportsystem in the fault to a suitable trap where it will accumulate. Theintegrated transport ability of a fault transport system can beevaluated as the contribution to gas reservoir accumulation by thefault transport system; this is known as fault transportability (FTA).FTA is defined according to all of the parameters (mentioned above)that influence the transportability in a fault, while also consideringthe difficulty of the gas's passing through the faulted region andeffective transporting space inside the faulted region.

FTA ¼Pn

i¼1ðTi�Li�hi�tiÞðЧ i�sinqiÞ

In this equation, n is the number of gas source faults in a gasfield, and h/sinɵ is the vertical extension length of the fault. T can becalculated from the displacement, as described above, and T*L*h/sinɵ represents the volume of the fault. The larger the volume of thefault, the larger the amount of natural gas carried by the fault, andthe better the transport conditions that can be provided. The faultvolume is multiplied by the fault activity time (t) and then dividedby the gas flow viscosity (m), so the evaluation of the FTA of gas

Table 2Elevation, Pressure, Gas density and Fluid Potential from the Bashijiqike formation in th

Well Name Elevation(m) Pressure(MPa)

KL2 �2147.48 74.190KL201 �2455.47 74.410KS1 �5321.82 116.495KS201 �5153.12 115.665KS203 �5324.02 115.934KS205 �5466.97 116.660KS3 �5265.75 115.638KS8 �5319.20 122.450KS801 �5604.40 122.720KS802 �5718.70 123.180KS8003 �5204.80 121.530KS806 �5441.30 122.030KS9 �5926.12 127.440KS902 �6233.30 125.720KS904 �6203.67 125.580KS13 �5903.74 133.217

source faults for natural gas weights each gas source fault by thefault dimensions, transporting time and resistance.

The higher the FTA value, the better the transportability of thegas source fault and the greater the contribution by that faulttransport system will be. A lower FTA would indicate a lowertransporting ability of the gas source fault and a lesser contributionfrom that fault transport system. The FTA is an aggregativeparameter that can be applied to estimate the transporting abilityof a given gas source fault.

4. Results

4.1. Natural gas geochemical characteristics

The major component of natural gas from the Keshen structuralbelt, Kuqa depression is alkane gas with a high content of methaneand low contents of heavier hydrocarbons. The content of non-hydrocarbon gases, including N2 and CO2, is extremely low, lessthan 2%. The composition of the natural gas does not vary muchthroughout the whole Keshen structural belt. The content ofmethane is greater than 97%, and that of ethane is from 0.2% to 0.8%.The dryness coefficients are higher than 0.99 (Table 1). The value ofiC4/nC4 is from0.400 to 1.700. The KL203well has the highest value,and the KS9 well has the highest value.

4.2. Fluid potential

Regarding fluid potential, this research focuses on the calcula-tion and analysis of the gas potential. Three major parameters,elevation, reservoir pressure, and natural gas density, are measuredat 18 typical wells in this research region (Table 2), and a fourth

e Keshen structural belt, Kuqa depression, Tarim Basin, China.

Gas density(kg/m3) Fluid Potential (m2/s2)

0.3950 21424.9480.3875 24446.9020.5297 52656.7860.5266 51000.3240.5145 52677.3450.5652 54081.0070.5249 52105.1750.5463 52641.6990.5604 55439.9820.5470 56562.0660.5525 51517.8240.5453 53838.7660.5687 58604.1540.6410 61614.6680.7174 61323.7580.5876 58394.181

Table 4Stable carbon isotope ratios of gases from Bashijiqike formation, Kuqa depression,Tarim Basin, China.

Well Strata Depth(m) d13C(PDB),‰

d13C1 d13C2 d13C3 d13C4

KL2 K1bs 3888e3895 �27.8 �19 / /KL201 K1bs 3630e4021 �27.2 �18.5 �19.5 �20.9KL201 K1bs 3770e3795 �27.2 �17.9 �19.1 �20.6KL201 K1bs 3936e3938 �26.2 �18.1 �19.1 �22.1KL201 K1bs 4016e4021 �27.3 �19 �19.5 �20.9KS102 K1bs 7210e7331 �29.3 �25.8 �25.1 /KS2 K1bs 6573e6697 �28.3 �17.7 �15.7 /KS5 K1bs 6703e6742 �26.5 �17.8 �19.2 /

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131 125

major parameter, gas potential, at these 18 measurement spots arethen calculated. As the measurement spots are distributed in deepand ultra-deep layers with an extra high pressure from 70 MPa to140 MPa, the natural gas density is lower than that measured atregular pressure and temperature. Three measurement spots in theKeshen9 well area have the highest gas potential, 21424.948 m2/s2,and two measurement spots in the Kela2 well area have the lowestgas potential, 61614.668 m2/s2. The measurement depths andreservoir pressures have clear effects on the gas potential. A greaterpressure or depth during the measurement is associated with ahigher gas potential (Table 2).

4.3. Gas transportation ability of gas source fault

According to the geostatistical analysis of the parameters relatedtomigrationwithin a gas source fault, under the circumstance of anapproximate natural gas viscosity and migration time, the changesin fault dimensions play an important role in the gas fault migrationability. For example, the Kela2 trap gas source fault has a relativelylarge fault displacement and fault vertical extension distance withthe other parameters in normal ranges, which causes a relativelylarge calculated gas source fault transport ability; in addition, forthe Keshen9 trap, although the fault extension distance is long, therest of the geological parameters are smaller compared with thenormal ranges, so the calculated gas source fault transport ability issmall (Table 3). All in all, the gas source faults in the Kela2 trap havethe greatest transport ability, followed by the Keshen6, Keshen13,Keshen2, Keshen8, and Keshen9 traps; the smallest is the Keshen12trap gas source fault.

5. Discussion

5.1. Gas-source correlation

Clarification of the sources of natural gas should be prior to thediscussion of the effectiveness of gas migration in the study area.There are numerous of previous studies regarding the source ofnatural gas in the Kuqa area (Zhuo et al., 2011; Lu et al., 2012; Guoet al., 2012), all of which agree that the gas is highly and overlymatured coal gas from Jurassic coal-related source rock (Zhanget al., 2011; Dai et al., 2005) and Triassic source rock of lagoonfacies.

Gas-source correlation was studied based on geochemicalcharacteristics of source rocks and gas. Thewhole Keshen structuralbelt has two series of source rock developed, including Triassic andJurassic, which are thick, widely distributed and rich in organic

Table 3Fault migration geological parameters in the Keshen structure belt of the Kuqa depressio

Trap Name Fault Fault Displacement(H)km

Fault ZoneWidth (T)km

Fault ExtensionLength (L)km

KL2 KL2N 1.4 0.8 23KL2S 3.2 1.7 25

KS6 KL6N 3.2 1.7 25KS6S 0.7 0.5 25

KS2 KS2N 0.7 0.5 20KS2S 0.5 0.3 20

KS8 KS8N 0.5 0.3 24KS8S 0.8 0.5 24

KS9 KS9N 0.8 0.5 28KS9S 0.5 0.4 28

KS12 KS12N 0.5 0.4 16KS12S 1.0 0.6 16

KS13 KS13N 1.0 0.6 23KS13S 1.2 0.7 23

matter. The source rock has dark mudstone with a TOC fromapproximately 1.2%e4% and carbargilite from 15% to 25% (in someparts, over 25%). The organic matter in the source rock is mainlyType III, which is the main generator of gas (Qin et al., 2007; Zhuet al., 2012). The reflectance of vitrinite (Ro) is from 0.56% to2.30%. This type of coal-measure source rock with rich organicmatter abundance and high maturity is the critical material foun-dation for the richness in natural gas of the Keshen structural belt,Kuqa depression.

The carbon isotopes of the Keshen structural belt are in thefollowing order of prevalence: d13C1 < d13C2 > d13C3 > d13C4(Table 4). d13C2 is one of the most important indicators used todistinguish oil-related gas (oil gas) from coal-related gas (coal gas).Previous studies have established a series of criteria used todifferentiate between them (Dai et al., 2005, 2008). According tothis research, natural gas from the Keshen structural belt, which hasd13C2 values from d17.5‰ to �26‰ (Table 4), is a coal-related gas.

According to these descriptions and analyses of the source rockand natural gas properties, the gas gathered in the deep and ultra-deep layers of the Bashijiqike formation in the Keshen structuralbelt, Kuqa depression, comes from Jurassic and Triassic humus-typedark mudstone with high maturity.

5.2. Advantage direction of natural gas migration controlled byfluid potential and geochemical tracing

The split groove in the fluid potential field is a boundary linethat controls the oil and gas migration pathway, and this line isdetermined by the shape of the isolines in the fluid potential field inthe delivery bed. By analogy, as mountains separate watersheds indifferent geographical locations or river systems, a split groove

n in the Tarim Basin, China.

Fault VerticalDistance (h)km

FaultDip (ɵ)

Gas Viscosity(m)mPa.s

MigrationTime (t)Ma

FTA

2.300 0.860 0.035 3 16219.072.300 0.872 0.035 32.300 0.872 0.037 2 7671.821.100 0.850 0.037 21.100 0.850 0.039 2 1117.651.000 0.842 0.039 21.000 0.842 0.041 2 1030.050.700 0.845 0.041 20.700 0.845 0.041 2 884.440.405 0.835 0.041 20.405 0.835 0.041 2 699.210.800 0.856 0.041 20.800 0.856 0.041 2 1647.100.800 0.860 0.041 2

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131126

separates different oil and gas accumulation and migration units.The gas and oil on the two sides migrate in two different directionsto two different zones. When the oil and gas supply is in normalconditions, it is unlikely to cross the split groove to migrate andaccumulate from different zones. Therefore, zones surrounded by a

Fig. 5. Hydrocarbon migration analysis using fluid potential distribution features in the Keshmap for the Bashijiqike Formation in the Keshen structural belt of the Kuqa depression.accumulation direction in the Keshen structural belt of the Kuqa depression.

split groove are relatively independent accumulation systems(units), and the oil and gas in the system tend to have a similaraccumulation direction and part. Almost no migration or exchangeof oil and gas occurs in different systems, so it is difficult for oil andgas in a single part to accumulate (Liu et al., 2002; Pang et al., 2013;

en structural belt of the Kuqa depression, Tarim Basin, China. (a) Fluid potential contour(b) Fluid potential contour section map in the Keshen structural belt, showing the

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131 127

Peng et al., 2016).In the Keshen structural zone, Kuqa depression, Tarim Basin,

China, the relatively independent natural gas migration system isnot only controlled by isolines in the fluid potential field but alsoqualified by thrust faults that form a boundary. The independentaccumulation units that have such a boundary on the Keshenstructural belt can be divided into seven parts (Fig. 5a). On everysingle independent block, natural gas migrates to reservoirs fromthe source rocks through faults (Fig. 5a). Setting the three faultblocks that cross Kela2, Keshen2, and Keshen8 as an example, Kela2has the smallest value for the fluid potential, followed by Keshen8,and Keshen2 has the greatest value in the Bashijikqike formation.To further discuss the relationship between the fluid potential andnatural gas preference migration pathway, this study introduced arelatively complete geochemical parameter, the ratio of n-butane toiso-butane (iC4/nC4). Natural gas migration causes the relativeenrichment of iso-paraffin and loss of n-alkanes, which increasesthe ratio of n-butane to iso-butane (iC4/nC4) (Chen and Li, 1994).According to (Fig. 5b) it is obvious that the Kela2 fault block has thehighest iC4/nC4, followed by Keshen6, and Keshen2 is the smallest.Therefore, natural gas accumulates preferentially in the low fluid

Fig. 6. Burial history and inclusion features of a typical gas-condensate reserv

potential direction in the process of gas vertical migration. By thatanalogy, in the 7 main independent accumulation units in theKeshen structural belt, Kuche depression, natural gas first migratesin Kela2, then in Keshen6, followed by Keshen8, Keshen2, Keshen9,and Keshen13. The Keshen12 block will be discussed later becauseit has only one development well and no industrial gas at present.

5.3. Gas source fault contributions to gas accumulation aredetermined by gas transport ability of the gas source faults

In addition to the calculation principle, the selection of param-eters and the calculation method, the application conditions of theFTA should be described here. Firstly, as we have mentioned in theintroduction, the study area is in foreland thrust belt with largefaults connecting source rocks and reservoirs. Then, the peak valueof the natural gas inclusions homogenization temperature is from140� to 160� corresponding to nearly 2 Ma by the burial historycurves in the Keshen structural belt (Fig. 6), which means that theonly gas accumulation time in the Keshen structural belt is 2 Ma.Thus, in the study area, the influences of multiple stages of thehydrocarbon transportation and accumulation are negligible, and

oir the Keshen structural belt of the Kuqa depression, Tarim Basin, China.

Fig. 7. Map of gas source faults in the Keshen structural belt of the Kuqa depression, Tarim Basin.

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131128

as a result, the quantitative evaluation of fault transporting capacityis more reasonable.

There are eight primary gas source faults in the Keshen struc-tural zone of the Kuqa depression (Fig. 7). These faults provide themain natural gas migration pathways, and play an important role informing the gas reservoir in the Keshen structural belt.

Among the seven primary traps that have been developed atpresent, the fault conducting contribution values are relatively highin two zones (Fig. 8), one located on the Kela2 trap where the Kela2well is located and the other on the Keshen6 trap footwall that isopposite Kela2; Because the two traps are located on the hangingwall and foot wall in the reverse fault, the Keshen6 trap can onlypartially be displayed in the map (Fig. 9). For the Keshen structuralbelt, the fault transport contribution value to the gas reservoir

Fig. 8. Histogram showing FTA in the Keshen struc

basically belongs to one interval and has a tendency to increase andlater decrease from north to south (Fig. 9), which indicates that thegas source faults that act as the dominant vertical migrationpathways of the whole Keshen structural belt show differencesbetween the south and north, which leads to the differences in theeffectiveness of forming different gas reservoirs controlled bydifferent gas source faults.

The author chose the reserve abundance in gas reservoirs as animportant assessment index to evaluate the gas accumulation ef-ficiency and demonstrate its relationship with the fault conductingvalue. The reserve abundance is related to the transport contribu-tion value of the gas source faults in the corresponding gas reser-voirs (Fig. 10). Higher transport contribution values reflect greatergas reserve abundances. This result explains that when gas

tural belt of the Kuqa depression, Tarim Basin.

Fig. 9. FTA distribution map in the Keshen structural belt of the Kuqa depression.

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131 129

reservoirs are under the same structural background and accu-mulation condition, the contribution value of the gas source faultsto the reservoir accumulation is the main influence factor in thedifference of the accumulation efficiency.

6. Conclusions

In the end, after a comprehensive consideration and evaluationof the effectiveness of natural gas migration in seven main deepand ultra-deep tight sandstone gas reservoirs on the whole Keshenstructural belt, the following conclusions were reached:

Fig. 10. Map showing the relationship between the FTA and reserve abunda

(1) The major sources of natural gas in deep and ultra-deep tightsandstone gas reservoirs in the Keshen structural belt, Kuqadepression are Triassic and Jurassic source rocks.

(2) In the seven major independent units of migration andaccumulation of the Keshen structural belt, Kuqa depres-sion, the predominant accumulation directions of naturalgas are towards tectonic units with lower fluid potentials.The faulted block with the highest priority during accu-mulation is the Kela2 trap, followed by the Keshen6 trap,Keshen8 trap, Keshen2 trap, Keshen9 trap, and Keshen13trap, in that order.

nce in the Keshen structural belt of the Kuqa depression, Tarim Basin.

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131130

(3) As the major vertical transport path of gas source faults of adeep and ultra-deep tight sandstone gas reservoir in theKeshen structural belt, Kuqa depression, there is diversity inthe zoning of the polar direction. The greater the contribu-tion from a gas source fault during transport is, the better theresulting gas migration and accumulation.

(4) The Kela2 gas reservoir has the highest effectiveness ofmigration within the entire deep and ultra-deep tightsandstone gas reservoir in the Keshen structural belt, Kuqadepression followed by the Keshen6 trap, Keshen8 trap,Keshen2 trap, Keshen13 trap, and Keshen9 trap, in that order.

The evaluation method of gas migration effectiveness discussedin this paper can be applied to similar gas reservoirs in the similartectonic background. Moreover, it can not only guide the wholeexploration of the deep and ultra-deep tight sandstone gas reser-voirs in the foreland thrust belt of Kuqa depression, but also can beapplied to exploration of similar gas reservoirs in the similar tec-tonic background, and can improve the exploration efficiency in acertain range.

Acknowledgements

This work was supported by the National Natural ScienceFoundation of China (Grant No.41572100 & No.41372146) and Na-tional Major Petroleum Projects (No.2017ZX05008-003-010). Wethank the Tarim Oilfield Company of CNPC China, Ltd., for providingbackground geological data and permission to publish the results.

References

Aydin, A., 2000. Fractures, faults, and hydrocarbon entrapment, migration and flow.Mar. Pet.Geol. 17, 797e814. http://dx.doi.org/10.1016/S0264-8172(00)00020-9.

Chen, A.D., Li, J.F., 1994. Study on geochemical indexes of natural gas migration. Nat.Gas. Geosci. 5 (4), 38e67 (in Chinese).

Chen, J.Q., Jiang, Z.X., Pang, H., Pang, X.Q., 2014. Lateral migration of petroleum inthe jurassic toutunhe formation in the fudong slope, junggar basin, China.Resour. Geol. 64, 35e46. http://dx.doi.org/10.1111/rge.12025.

Colombo, U., Gazzarrini, F., Gonfiantini, R., Tongiorgi, E., Caflisch, L., 1969. Carbonisotopic study of hydrocarbons in Italian natural gas. Adv. Org. Geochem 43 (6),499e516.

Dai, J.X., Li, J., Ding, W.W., Hu, G.Y., Luo, X., Tao, S.Z., Zhang, W.Z., Zhu, G.Y., Mi, J.K.,2005. Geochemical characters of the giant gas accumulations with over onehundred billion cubic meters reserves in China. Pet. Explor. Dev. 32 (4), 16e23(in Chinese with English abstract).

Dai, J.X., Ni, Y.Y., Wu, X.Q., 2012. Tight gas in China and its significance in explo-ration and exploitation. Pet. Explor. Dev. 39 (3), 257e264 (in Chinese withEnglish abstract).

Dai, J.X., Zou, C.N., Zhang, S.C., Li, J., Ni, Y.Y., Hu, G.Y., Luo, X., Tao, S.Z., Zhu, G.Y.,Mi, J.K., Li, Z.S., Hu, P.A., Yang, C., Zhou, Q.H., Shuai, Y.H., Zhang, Y., Ma, C.H.,2008. Identification of organic and inorganic alkanes. Sci. China, Ser. D. EarthSci. 38 (11), 1329e1341.

Davis, J.S., 2011. Modeling Gas Migration, Distribution, and Saturation in a Struc-turally and Petrologically Evolving Tight Gas Reservoir. IPTC, Bangkok, Thailand.

Elkins, L.E., 1978. The Technology and Economics of Gas Recovery from Tight Sands.SPE Production Technology Symposium, New Mexico.

England, W.A., Mackenzie, A.S., Mann, O.M., Quigley, T.M., 1987. The movement andentrapment of petroleum fluids in the subsurface. J. Geol. Soc. 144, 327e347.http://dx.doi.org/10.1144/gsjgs.144.2.0327.

Fu, J.M., Liu, D.H., 1992. The Natural Gas Migration, Reservoir and Capping Condi-tions. Science Press, pp. 83e88 (in Chinese).

Guan, D.S., Niu, J.Y., Guo, L.N., Xu, H.Z., 1995. Unconventional Oil and Gas Geology inChina. Petroleum Industry Press, Beijing, pp. 12e40 (in Chinese).

Guo, J.G., Pang, X.Q., Liu, D.D., Jiang, Z.X., Jiang, F.J., 2012. Hydrocarbon expulsion forMiddle-Lower Jurassic coal measures and evaluation of potential resource inKuqa depression. Nat. Gas. Geosci. 23 (2), 327e334 (in Chinese with Englishabstract).

Hayward, N., Watts, A.B., Westbrook, G.K., Collier, J.S., 1999. A seismic reflection andGLORIA study of compressional deformation in the Gorringe Bank region,eastern North Atlantic. Geophys. J. Int. 138 (3), 831e850.

Hooper, E.C.D., 1991. Fluid migration along growth faults in compacting sediments.J. Pet. Geol. 14, 161e180.

Hubbert, M.K., 1953. Entrapment of petroleum under hydrodynamic conditions.AAPG Bull. 37, 1954e2026.

Hull, J., 1988. Thickness-displacement relationships for deformation zones. J. Struct.

Geol. 10 (4), 431e435.Jia, C.Z., Li, Q.M., 2008. Petroleum geology of Kela-2, the most productive gas field in

China. Mar. Pet. Geol. 25 (4), 335e343.Li, J.Z., Zheng, M., Zhang, G.S., Yang, T., Wang, S.J., Dong, D.Z., Wu, X.Z., Qu, H.,

Chen, X.M., 2012a. Potential and prospect of conventional and unconventionalnatural gas resource in China. Acta Pet. Sin 33 (S1), 89e98 (in Chinese withEnglish abstract).

Li, J.Z., Guo, B.C., Zheng, M., Yang, T., 2012b. Main types, geological features andresource potential of tight sandstone gas in China. Nat. Gas. Geosci. 23 (4),607e615 (in Chinese with English abstract).

Liang, D.G., Zhang, S.C., Chen, J.P., Wang, F.Y., Wang, P.R., 2003. Organic geochem-istry of oil and gas in the Kuqa depression, Tarim Basin, NW China. Org. Geo-chem 34 (7), 873e888.

Liu, X.D., Xu, J.Z., Li, C., Yu, S.J., 2002. Automatic definition of compartition troughsand accumulation unies based on the fluid potential. Chin. J. Geol. 37 (3),295e301 (in Chinese with English abstract).

Losh, S., Eglington, L., Schoell, M., Wood, J., 1999. Vertical and lateral fluid flowrelated to a large growth fault, south Eugene Island Block 330, offshore Loui-siana. AAPG Bull. 83, 244e276.

Lu, X.S., Jiang, Y.L., Song, Y., 2007. Influence of mechanical properties and stress stateof caprock on its sealing performance: taking Kela-2 gas field as an example.Nat. Gas. Ind. 27 (8), 48e51 (in Chinese with English abstract).

Lu, X.S., Liu, K.Y., Zhuo, Q.G., Zhao, M.J., Liu, S.B., Fang, S.H., 2012. Palaeo-fluid evi-dence for the multi-stage hydrocarbon charges in Kela-2 gas field, Kuqa fore-land basin, Tarim Basin. Pet. Explor. Dev. 39 (5), 537e544 (in Chinese withEnglish abstract).

Ma, Y.S., Cai, X.Y., Zhao, P.R., 2011. The research status and advances in porosityevolution and diagenesis of deep carbonate reservoir. Earth Sci. Front. 18 (4),181e192 (in Chinese with English abstract).

Macavoy, P.W., 1979. Natural gas policy act of 1978. Nat. Resour. J. 19, 4.Magoon, L.B., Dow, W.G., 1994. The petroleum system-from source to trap. AAPG

Mem. 644.Pang, H., Chen, J.Q., Pang, X.Q., Liu, K.Y., Liu, L.F., Xiang, C.F., Li, S.M., 2013. Analysis of

secondary migration of hydrocarbons in the Ordovician carbonate reservoirs inthe Tazhong uplift, Tarim Basin, China. AAPG Bull. 97, 1765e1783. http://dx.doi.org/10.1306/04231312099.

Peng, J.W., Pang, X.Q., Xiao, S., Peng, H.J., Li, Q.W., Song, S., Wu, L.Y., Chen, D., Hu, T.,2016. Secondary migration of hydrocarbons in the zhujiang formation in thehuixi half-graben, pearl river mouth basin, south China sea. Can. J. Earth Sci. 53(2), 189e201.

Philippi, G.T., 1965. On the depth, time and mechanism of petroleum generation.Geochim. Cosmochim. Acta 29 (9), 1021e1049.

Qin, S.F., Dai, J.X., 2006. Distribution of coal-derived oil and gas in Kuqa depressionand its control factors. Nat. Gas. Ind. 26 (3), 16e18 (in Chinese with Englishabstract).

Qin, S.F., Dai, J.X., L, X.W., 2007. The controlling factors of oil and gas generationfrom coal in the Kuqa depression of Tarim Basin, China. Int. J. Coal Geol. 70(1e3), 255e263.

Schmoker, J.W., 2002. Resource-assessment perspectives for unconventional gassystems. AAPG Bull. 86 (11), 1993e1999.

Schoell, M., 1983. Genetic characterization of natural gases. AAPG Bull. 43 (6),499e516.

Scholz, C.H., Sykes, L.R., Aggarwal, Y.P., 1973. Earthquake prediction: a physical basis.Science 181, 803e810.

Shamsuddin, A.H.M., Khan, S.I., 1991. Geochemical criteria of migration of naturalgases in the Miocene sediments of the Bengal Foredeep, Bangladesh. J. Earth Sci.5 (1), 89e100.

Shen, P., Cui, Y.C., Wang, X.B., Liu, D.H., Shen, Q.X., Liu, W.J., 1991. Studies onGeochemical Characteristics of Gas-source Rock and Natural Gas and Mecha-nism of Genesis of Gas. Gansu Science and Technology Press, pp. 166e176 (inChinese).

Sibson, R.H., Moorre, J.M., Rankin, A.H., 1975. Seismic pumping-a hydrothermal fluidtransport mechanism. J. Geol. Soc. 131, 653e659.

Spencer, C.W., 1983. Geologic aspects of tight gas reservoirs in the rocky mountainregion. J. Pet. Technol. 37 (7), 1308e1314.

Sun, Y.H., Lu, Y.F., Fu, G., Fu, X.F., Zhang, X.Y., 2006. Evaluation method on trans-porting natural gas efficiency of faule transportation system and its application.Nat. Gas. Geosci. 17 (1), 73e77 (in Chinese with English abstract).

Tang, L.J., Yu, Y.X., Yang, W.J., Peng, G.X., Lei, G.L., Ma, Y.J., 2007. Paleo-uplifts and saltstructures and their influence on hydrocarbon accumulations in the Kuqadepression. Acta Geol. Sin. 81 (2), 145e150 (in Chinese with English abstract).

Wang, Z.M., 2014. Formation mechanism and enrichment regularities of Kelasusubsalt deep large gas field in Kuqa depression, Tarim Basin. Nat. Gas. Geosci. 25(2), 153e166. http://dx.doi.org/10.11764/j.issn.1672-1926.2014.02.0153 (in Chi-nese with English abstract).

Wang, Z.M., Li, Y., Xie, H.W., Neng, Y., 2016. Geological understanding on the for-mation of large-scale ultra-deep oil-gas field in Kuqa foreland basin. China Pet.Explor 21 (1), 37e43. http://dx.doi.org/10.3969/j.issn.1672-7703.2016.01.004 (inChinese with English abstract).

Zhang, G.Y., Ma, F., Liang, Y.B., Zhao, Z., Qin, Y.Q., Liu, X.B., Zhang, K.B., Ke, W.l, 2015.Domain and theory-technology progress of global deep oil & gas exploration.Acta Pet. Sin. 36 (9), 1156e1166. http://dx.doi.org/10.7623/syxb201509015 (inChinese with English abstract).

Zhang, S.C., Zhang, B., Zhu, G.Y., Wang, H.T., Li, Z.X., 2011. Geochemical evidence forcoal-derived hydrocarbons and their charge history in the dabei gas field, Kuqa

Y. Shen et al. / Journal of Natural Gas Science and Engineering 46 (2017) 119e131 131

thrust belt, Tarim Basin, NW China. Mar. Pet. Geol. 28, 1364e1375. http://dx.doi.org/10.1016/j.marpetgeo.2011.02.006.

Zhao, L.S., Cen, K., Ye, R., 2000. Dynamic simulation of the uplifting pipe flow ofhydrothermal fluid by tectonic pumping and its prediction significance. EarthSci. Front. 7 (1), 205e215 (in Chinese with English abstract).

Zhao, W.Z., Zhang, S.C., Wang, F.Y., Cramer, B., Chen, J.P., Sun, Y.G., Zhang, B.M.,Zhao, M.J., 2005. Gas systems in the Kuche Depression of the Tarim Basin:source rock distributions, generation kinetics and gas accumulation history.Org. Geochem 36 (12), 1583e1601.

Zhu, G.Y., Yang, H.J., Zhang, B., Su, J., Chen, L., Lu, Y.H., Liu, X.W., 2012. The geologicalfeature and origin of Dina 2 large gas field in Kuqa depression, Tarim Basin. ActaPetrol. Sin. 28 (8), 2479e2492 (in Chinese with English abstract).

Zhuo, Q.G., Li, Y., Song, Y., Yang, X.Z., Zhao, M.J., Fang, S.H., Liu, S.B., Lu, X.S., 2013.Evolution of paleogene saline deposits and effectiveness of traps in Kelasutectonic zone, Kuqa depression, Tarim Basin. Pet. Geol. Exp. 35 (1), 42e47.http://dx.doi.org/10.11781/sysydz20130107 (in Chinese with English abstract).

Zhuo, Q.G., Zhao, M.J., Li, Y., Wang, Y., 2014. Dynamic sealing evolution and hy-drocarbon accumulation of evaporite cap rocks: an example from Kuqa Fore-land Basin Thrust Belt. Acta Pet. Sin. 35 (5), 847e856. http://dx.doi.org/10.7623/syxb201405004 (in Chinese with English abstract).

Zhuo, Q.G., Zhao, M.J., Xie, H.W., Fang, S.H., Li, M., 2011. Relationship betweenreservoir bitumen and hydrocarbon migration in Dabei region, Kuqa ForelandBasin. Pet. Geol. Exp. 33 (2), 193e196 (in Chinese with English abstract).

本文献由“学霸图书馆-文献云下载”收集自网络，仅供学习交流使用。

学霸图书馆（www.xuebalib.com）是一个“整合众多图书馆数据库资源，

提供一站式文献检索和下载服务”的24 小时在线不限IP

图书馆。

图书馆致力于便利、促进学习与科研，提供最强文献下载服务。

图书馆导航：

图书馆首页 文献云下载 图书馆入口 外文数据库大全 疑难文献辅助工具