Name: Reband Azad Raza

Petroleum Engineering Department/ Drilling Engineering II

Date: 23 03 2016

(Is gas migration problem in petroleum industry?)

petroleum industry looking forward to be safe and reliable industry, one of most common

problems petroleum industry faced since it’s development it’s (gas migration) Gas migration

also called gas communication or gas leakage (Carter and Slagle, 1970) gas migration is the

most frequent, and no doubt the most critical and dangerous (faul, 10 Dec 1984) , as the

beginning of industry the gas migration wasn’t detectable due to complex of reservoir and

inefficient technology, Gas migration is most common drilling problems, it’s occurs when

gas invasion migrate from High pressure zone[formation] to lower pressure

zone[wellbore],the gas migration can cause the well severity problems like blowout when the

well all in lost due to imbalanced pressure all and when it’s cement running or while drilling

running on, the detecting gas migration down hole it’s not such easy way to try, the detection

always running on the well’s surface by checking the pressure regulators and well control

monitors or by increase Flow rate or increase in mud pits and having flow while Mud Pumps

shut down, there are several cause and predictable ways to prevent gas migration, one of such

factors is [density],Controlling density immediately after cementing it’s so similar to well

control after drilling, if the [hydrostatic pressure] decrease below the formation gas pressure

will cause [gas kick], must assure that the pressure at critical zones is maintained between the

pore and the fracturing pressure at all times during, and immediately after, the cement job

(Parcevaux, Step 6 1984), density must be carefully and correctly to be designed to prevent

gas flow during cement displacement (Bonett, Spring 1996), although the design must care

of danger of losing circulation, any density went wrong made while mixing a slurry on the

surface may causes large changes in slurry properties ,that is why now modern mixing

cement systems will offers accurate density control, and the Mud can be a good character For

preventing gas migration, There is no easy path for gas if good mud exists in the well bore,

drawn water from [Mud cake] to surface of [cement sheath], this can causes of cracking in

the mud cake which is causes the best route for gas migration, for example if thick mud cake

dehydrates by 14 % it will make (0.195 mm cracks) in the mud cake at the sidewall of the

well bore (NELSON, 1990), and another threat it’s while when the cement slurry begins to

set, the hydrostatic pressure quickly approaches zero (Levine .D, 1979), due to separation of

both of fluids and pore from connecting each other that makes to separate system , because

the fluids in the wellbore cannot have force on the well bore’s wall that why hydrostatic

approach to zero, one of the solutions it’s using surfactants with cement slurry, the surfactants

will enter gas zones to become a foam, and by using a [bentonite][sulphate salts] to control

Gel-strength of cement to prevent Gas sneak, there is also a physical ways to prevent Gas

migration, by setting a Casing Packers.

ReferencesBonett, A., Spring 1996. Oil Field Review. Schlumbeger[online], p. 4.

Carter and Slagle, 1970. A Study of Completion Practices. SPE 764, p. 5.

faul, s., 10 Dec 1984. Annular Gas Flow Theory and Prevention. Oil&gas J, pp. 84-112.

Levine .D, T. .., 1979. AnnularGas Flow After Cementing: A Look ;it Practical Solutions, s.l.: paper spe 8255.

NELSON, E. B., 1990. Well Cemening. Saint-Etienne, France: Elisiver .

Parcevaux, D. a., Step 6 1984. Mechanisms of Gas Channeling During Primary Cementation-Methods for Prevention and Repair. newyork: Chemische Produkte in der Erdolgewinnung,Clausthal-Zellerfeld.