Reservoir Damage Evaluation And P Rotective Measur Es Under High Temperature And High Pressure Of Lun Nan Area,Tarim Oilfield

In our country,low-permeability oil and gas field exploration and development attracts more and more attention. Tarim Oilfield in Lunnan area is a typical low porosity,permeability reservoirs.It is very vulnerable due to the particularly of this type reservoirs,especially the existence of small pore throat radius,strong heterogeneity,big impact of muddy,development of micro-cracks. A large number of reservoir protection experiment has been done in this area at normal temperature and pressure,and could not restore its true formation conditions of reservoir damage, and hardly to put forward targeted reservoir protection measures.Therefore,we should study this reservoir’s damage in the enviroment of simulated geological condition. Optimizing new low-damage drilling and completion fluid system,forming reservoir damage evaluation technology and drilling and completion fluid system which is suitable in Lunnan area is extremely urgent. What’s more, it has achieved remarkable results in field test.In this paper, we carried out comprehensive anlysis method of core observation, thin section analysis, sensitivity tests, and simulate the real geological conditions of formation damage evaluation system, studied reservoir damage factors in simulated geological layer, and make clear of Lunnan oilfield reservoir damage degrees and its mechanism.As the geological layer of Jurassic speed sensitive is weak, Triassic strata speed sensitivity is weak to moderate, Jurassic formation water sensitivity is weak to medium,Triassic water sensitivity is weak, Jurassic and Triassic strata sensitivity to salt are moderate. We have excogitated specific measures to prevent the injury of five sensitive through anti-swelling agent to pre-wash before the water injection,taking acidification in Jurassic and Triassic strata with soil acid or hydrochloric acid (20%-30%), to inject pH of the water should be controlled below the critical alkalinity values in water injection development process.Dim at drilling fluids, completion fluids, perforating fluids to do a dynamic reservoir damage assessment experiments to calculate the damage rate of the core permeability before and after the working fluid is injected, and then given the measures of protection strata according to the respective damage mechanismthrough simulate formation conditions by SY-core T5336(2006) analysis method to (high pressure40Mpa, temperature120℃) in five main reservoir wells:LN2-3-1well,LN3well,LN203well,LN2-2-J1well,LN2-4-J2well. For the drilling fluid, it is recommended that to add2%FLOCAT (fluid loss additive)+3%+2%LOCKSEAL (film blocking agent) based on original drilling fluid. For the part of perforation fluid, adding clay compound stabilizers, that is adding2%poly-amine (clay stabilizer)+2%of NH4Cl on the basis of the original perforating fluid. To solve the contamination of completion fluid with acidic, try to use12%the HCI+1%of HF mud acid combination which has has the feature of delay the reaction rate of acid rock.