| Xishanyao Formation of Cai 9 well block is an ultra low reservoir with compl icated geological conditions.Part of the regions is natural microcrack developed with the serious phenomenon of water sensitivity.In the early phase of the devel opment process,because of the unclear understanding of the reservoir geological characteristics,we took the large well spacing development,intensive injection and production and ignored the water flooding policy,leading to a low currentrate of oil production and poor development effect.By'September 30,2011,58 oil wells have been opened in Xishanyao formation in Cai 9,accounting for only a quarter of the total number.Large areas of oil wells have been closed with low utrlization ratio.At present,the degree of reserve recovery in the area is 22.5%,and the comprehensive water cut is 88.2%,with water cut less than 60% in 25% of the oil wells and larger than 80% in 57% of the oil wells.Injection and produ ction contradiction further aggravates,its overall differential pressure gradually in creases to over 10 MPa,pressure field distribution is cxtremely uneven,water br eaks through in oil wells,the situation of high water cut and being short of feed flow coexists.In order to improve the effect of reservoir development and economic benefits,we have used modern reservoir engineering methods,system engineering theory and optimization method to adjust,forecast,analyze and optimize the design of the injection-production program.This study is tracking the study of previous projects.Through detailed investigation and study,we have mastered the structure characteristics of the of the target reservoir,sedimentary characteristics,reservoir characteristics,fluid characteristics,temperature and pressure system,reservoir types and characteristics of geological reserves,etc.Besides,we have studied the development situation of Cai 9 wellblock respectively from the production and reserve-production balance conditions,liquid producing capacity and moisture content changes,injection-production ratio balance,maintain condition,water drive energy with the degree of reserves,measures to increase production conditions,We also analyzed the main problems existing at present,including the seepage ability,the serious well water flooded and water channeling,the poor adaptability of injection-production well pattern.Combined with reservoir development situation,we have put forward the small well spacing injection-production decision and the basis of selecting the encryption district.After comparied the field tracer test,interference well test,dynamic connectivity research situation with the work situation of well water breakthrough,we can find that the fracture distribution of Encryption area are very complicated and it is very difficult to inject and product based on water flooding.Through numerical simulation method,we optimize the solution of“ Extract+fracturing+cycle water injection” after we use the optimization method,we found that the optimized scheme obviously improve the cumulative oil production,effectively improve the economic benefit than before.Through the analysis of the logging results of infill well we found that Braden exists considerable remaining reserves with high Angle fracture development in the area.In view of this phenomenon and tough production market,we put forward three new ideas such as the air injection flooding,water alternating gas flooding and foam flooding... |
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