Research And Application On Well Cement Technology Of Salt And Gypsum Layer In Kenjiyak Oilfield

Kenjiyak Oilfield cement operation faces complex geological conditions:coverd with overlying thick salt-gypsum layer,burial depth,abnormal high pressure,fracture development,high gas oil ratio,high yield,sulphur,etc.It is easy to encounter leakage and pour out in drilling operation,cementing failure,well completion is difficult to complete,and so on.Due to high reservoir pressure,oil and gas is active,safe window is narrow,resulted in big difficulty of well completion,especially the oil layer cementing quality is a serious problem in oil production in oilfield.Gypsum,cream sandwiched between rock and plastic mudstone is reducing,expansion and the collapse of the plastic flow and part of the hole.The hole is irregular,blocked casing easily causing sticking,slurry displacement efficiency is low,the wellhead pressure of cementing operation is high,seriously affecting the cementing quality.Oil well cementing quality problem mainly were listed as the following:(1)the CBL logging display cement bond quality is poor,qualified rate is low.(2)ring up the air,in the 244.5 mm casing with 177.8 mm between oil layer casing pressure.The previous salt mud system and preflush cannot meet the needs of the site construction.In order to improve the cementing quality of the region and provide good foundation for the follow-up production,it is necessary to do some researches on the cementing process in the region.In this paper,analysis and study on how to improve the cementing technology of salt-gypsum layer,so that we analysis the north oil field geological characteristics and the block of exploration and development;combining with the cementing of the early stage of the situation at home and abroad,the current regional salt paste layer cementing existing technical problems and solving strategy,through the indoor experiment and theoretical analysis basically achieved the following results:(1)Developed a high density salt-resistant slurry system.Based on the research of the slurry salt resistance mechanism,using brine improving salt resistance of the cement slurry,forming a set of adjustable density,good stability,controlled water loss and so on the characteristic of high density salt slurry system.(2)Developed salt resistance preflush.Formation against kazakhstan in cream containing salt,salt paste and salt formation contain a variety of types of inorganic salt and concentration is higher,in order to maintain the salt layer of borehole wall stability to ensure cementing operation smoothly,at the same time in order to improve the displacement efficiency and cementing quality interface,using the theory of salt resistance to salt,the salt water as the base fluid,by suspending agent,surface active agent,retarder,fillers and other admixtures and additives on material selection,developed a set of compound salt resistant pad.(3)salt layer cementing matching technology is developed.Aiming at the difficulty of the cementing of salt layer,improve the displacement efficiency of large size casing,maintain the cementing salt layer in the construction of borehole wall stability,gas channeling prevention and so on are studied,by adopting inner string cementing technique improves the quality of the large size casing cementing,using the compound salt preflush,guarantee the stability of borehole wall and improve water mud displacement efficiency,using high density resistance to salt mud system ensure the quality of cementing salt layer,using high density salt channeling cement slurry system and tube Wai Feng isolation device to improve reservoir cementing quality preventing gas channeling and other cementing technology,form the supporting technology of salt well cementing technology.