Study On The Injection Pressure Limits For Casing Damage Prevention In Geo Complex Block Of The South-West ? Area

In the later period of oilfield development,the high pressure water injection is to improve the recovery rate of one of the measures,but for geological structure with the fault,mudstone interlayer and large dip angle strata oil blocks,high pressure water injection often caused water invasion fault activation,mud invasion water softening and inclined strata slip and other geological disasters,and will induce casing damage of oil and water wells which released in these strata,water well casing damage,having a significant impact on oil field development,resulting in serious economic losses.This paper contains faults,mudstone and big dip reservoirs with complicated geological structure fields,based on fluid solid coupling theory,established the mathematical model of fluid solid formation and interaction of the injection process of water flooding,then study the softening characteristics of mudstone in the fault activation zone and water intrusion conditions by the method of indoor in the experiment,and then studied the formation with big dip slip,mudstone invasion water softening and water intrusion fault activation conditions to avoid casing injection pressure limit using numerical simulation method,based on a two area of West Block Oilfield complicated geological structure mining examples,using numerical simulation method,studied the deformation of stratum in the process of mining and casing damage,put forward to avoid the casing injection pressure limit.The main work of this paper is as follows:(1)Based on Biot's consolidation theory,the coupling model of oil.water two.phase flow and stress is derived,and the mathematical model of coupling between seepage field and stress field in the process of water injection is established.(2)By interior ring shear test and three axis experiment under the condition of wetted fault activation zone,the relationship between the cohesive force,internal friction angle and residual strength of the fault zone and the water content and water saturation of the active zone is studied,establishing the function relationship;using the single axis test under the condition of wetted mudstone to study laminated mudstone in the elastic modulus and compressive strength under different moisture content,explore the regularity of imudstone exposure to water softening.(3)Take the western part of the Southern District 2 commonly used four water injection area group as an example,by using the numerical simulation method were studied well group in the four layer is simple,high dip angle strata,mudstone interlayer and near fault conditions in the course of water flooding formation and the casing should force and deformation of the distribution and development rules,four cases of water injection pressure limit for casing damage are proposed respectively.(4)According to the example of the complicated geological structure in the west block of the south two block,the Petrel geological model is transformed to the finite element mesh,based on the actual production parameters of oil exploitation for input conditions,study the strata deformation and casing in the process of mining damage using large-scale numerical simulation method,and with the actual casing damage statistical results were compared and analyzed,and put forward the preventing casing damage of injection pressure limit.