12. Horizontal Well Completion

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Topics Covered Planning the horizontal well

completion Horizontal well completion

techniques Equipping the horizontal well Working in the horizontal well

environment Logging and perforation

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Horizontal Well Completion• Horizontal well (HW) drilling is potentially the most

important completion technique since hydraulic fracturing

• HW is normally drilled vertically to a particular depth and horizontally to additional hundreds or thousands feet

• HW is classified based on its turning radius– R = 57.3/BUR (buildup rate, o/ft)– Three types: short, medium, and long-radius

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Completion of Horizontal Wells• HW completion depends on formation

characteristics, reservoir type, and drilling technique

• Formation characteristics: homogeneous or heterogeneous

• Reservoir type: gas or under-saturated or saturated or heavy oil

• Drilling technique: short or medium or long-radius method

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Completion Types• Two types: open hole and cased-cemented

completion• Open hole:can be true or pseudo open hole

– true OH in competent formation with no water or gas

– pseudo OH with slotted liners and/or ECP for isolation

• Cased-cemented hole– premium completion (very expensive)– need to perforate; last option

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Horizontal Open-Hole Completion

This is a true open hole completion and it is used in consolidated and competent formation with medium to high permeability

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Horizontal Perforated Liner Completion (pseudo open-hole)

The pre-perforated liner/casing is used where little or no stimulation is required, and the segmented uncemented liner/casing is used for open-hole evaluation of the wellbore and subsequent selective stimulation, if necessary.

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Horizontal Perforated Liner Completion (pseudo open-hole)

The pre-perforated liner/casing is used where little or no stimulation is required, and the segmented uncemented liner/casing is used for open-hole evaluation of the wellbore and subsequent selective stimulation, if necessary.

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Running of a horizontal pre-pack liner/screen

The slotted or pre-perforated liner/casing is used where little or no stimulation is required, and the segmented uncemented liner/casing is used for open-hole evaluation of the wellbore and subsequent selective stimulation, if necessary.

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Horizontal Well Selective Completion with ECP

External casing packers

The pre-perforated liner/casing is used here with some external casing packers (ECP). The ECPs are used for isolation of the hole segments that showed little or no production.

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Horizontal well cased and cemented liner completion

1. The cased and cemented completion is the premium completion approach. This means that the well must be perforated and stimulated.

2. Costs associated with these operations are so significant that there must be problems associated with the wellbore/formation combination that cannot be addressed in any other way

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Equipping the Horizontal Wells • Most tools are set with rotation movement, or hydraulic pressure,

which must be applied around the bend to the horizontal segment. Major tools are external casing packers (ECP), bridge plugs, packers, and artificial lift devices (pumping equipment)

• The tool size and operation are the most important parameters for the tools

– Length L, and diameter of the a rigid tool that can be run around the bend is a f(R)

– L = 1/6[R2 - (R -d)2]0.5; d = IDcasing - ODtool

– L = tool length, ft; R and d are in inches

• All tools are set by mechanical, or hydraulic or passive action. The movement required to set or unset a tool should be minimized.

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Effect of radius of curvature on the length of tool that can be run in a horizontal well

1. The length and diameter of a rigid tool that can be transported around a curve is dependent on the curve radius and the tool clearance.

2. The maximum length of any specific diameter of tool to be transported around a curve can be calculated using the equationL = 1/6[R2 - (R -d)2]0.5; d = IDcasing – ODtool; L = tool length, ft; R and d are in inches

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Multiphase flow patterns in a horizontal well

The dips and rises in the well profile act as down-hole separators for the various phases of the produced fluids, leading to slug flow

These slugs may be big enough to load up and kill the well. Thus, tubing should be landed at the low point in the lateral so as to minimize slugging.

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Figure 6.11 - Horizontal well perforation configuration in consolidated (360 phasing) and unconsolidated (120 - & 180 -

phasing) formations

Perforation of Horizontal Wells

Gun orientation - full phase (360o) in consolidated formations and 180o or 120o-phase in unconsolidated formations

Perforation density - use a lower shot density (2-shots/ft). This is because so much zone is exposed in horizontal wells plus perforating is expensive

Use bullet guns in low compressive formation and jet guns in high compressive formation

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Artificial Lift Equipment in HW

• These are gas lift, hydraulic jet, and electric submersible pumps

• Gas lift - a viable option in short and medium-radius, may be uneconomical in long-radius

• Hydraulic jet pumps - affected slightly by hole inclination but inefficient in low pressure wells

• Electric submersible pumps - not good in high angle wells and must be centralized. Also, very sensitive to high GOR. Have ability to lift large amount of fluids

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Working in Horizontal Well

• Hole cleaning - use high viscous pill or magnet

• Tubing stress at the bend - use flexible material

• Perforation

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Coiled Tubing Conveyed Logging Tools

• CT has three main parts: measuring tools and protection equipment, an electric connector between tool and drill pipe, and slide entry capability.

• It is important to prevent damage to cable by not lowering the slide entry sub beyond certain inclination or protect it by clamping along drill pipe.

1. Advantages: easy and rapid to use (significant reduction in rig time), accurate depth control, and the ability to make multiple runs.

2. Disadvantage: CT will buckle when the frictional forces associated with the guns in the horizontal hole exceed the CT critical buckling load. The advantages of CT are the speed of running the guns, the ability to log perforating guns on depth,

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Nitrogen kickoff of a well using coiled tubing

1. This figure shows one of the major applications of CT (nitrogen kickoff)

2. 25% of the CT business accounts for nitrogen kickoffs.

3. It is possible to pump N2 too fast Lighten column while RIH, then pump N2 at bottom of well

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HW Cementing Problems & Solutions

Three main problems: free-water on the upper side of well, deposition of solids, and inadequate fluid/cement displacement– Associated problems include mud and gas channeling

Solutions include the following:– Good cement and fluid design;(YP30 lbf/100 ft2)– Use mechanical devices - centralizers & scratchers– Use mechanical actions - rotate/reciprocate– Displace cement and fluid in turbulent flow

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A typical flow meter for production logging on coiled tubing

1. This figure shows another application of CT (production logging). The production profile of a horizontal well is often required for effective production management. To optimize well production, pressures and entry points of water, oil, and gas are the necessary data. One of the biggest problem is measuring and interpreting multiphase flow of the fluids especially in horizontal wells.

2. Two techniques have been developed to improve the quality of data measurement of two-phase flow in horizontal wells and to determine the location of fluid flux. These techniques, using CT, involve (a) a small variable-diameter metal petal-basket and a fluid analyzer tool, and (b) a temperature survey tool to measure temperature anomalies during production or injection of fluids.