Research Of The Sidetracking Selection Of Old Well In Su14 Well Area Of Sulige Gas Field

The old well sidetracking technology is an effective means to stabilize production and increase efficiency in the later stage of oil and gas field development.It not only avoids the repeated investment in new drilling or infill wells,but also can effectively reduce the development cost,perfect the pattern of development wells,and increase the production rate of single well and the degree of reserve production.It is able to excavate the potential of remaining recoverable reserves and improve the development effect of oil and gas reservoirs,and has a broad application prospect.This paper takes Su14 block of Sulige gas field as the research object,using multidisciplinary theory and method,based on the study of geological characteristics and development performance of gas reservoirs in this area,the distribution and potential area of remaining recoverable reserves are clarified.Based on the analysis of the development effect and the influencing factors of the existing sidetracking,the standard and method for selecting the optimum drilling position in the old well are established.The selection of sidetracking position,azimuth,well type,length and horizon of 3 wells in Su14 has been completed.The development index is predicted,which lays a foundation for tapping the potential of remaining reserves,improving the stable production capacity and developing effect.The main results achieved are as follows:(1)According to the logging data,core data and seismic data,the structure and trap characteristics,reservoir characteristics and gas reservoir characteristics are studied,and the gas reservoir reserves are calculated by volume method.The reservoir is characterized by low pressure,low permeability and low abundance.The gas-bearing area of Su14 is 169.80km~2,geological reserves is 241.42×10~8m~3 and reserves abundance is 1.42×10~8m~3/km~2.(2)On the basis of the study on the dynamic characteristics of the production in the Su14of the Soviet Union,the numerical simulation of gas reservoir in a typical well area is carried out on the basis of the three-dimensional fine geological model.Through the historical fitting of production dynamics,the distribution and potential region of remaining reserves are clarified.The total dynamic reserves in this area is 48.09×10~8m~3,and the production degree of gas reservoir is relatively low,and there is a great space for development adjustment,which can improve the development effect of gas reservoir through sidetracking of old well.(3)Based on the geological and production dynamic data of 6 sidetracking wells,the implementation effect is analyzed.The average daily output of 6 wells during the initial stage of sidetracking is 3.9×10~4m~3/d.At present,the daily output is 1.4×10~4m~3/d and the average cumulative gas output per well is 0.16×10~8m~3.The production condition,lateral drilling horizon,azimuth,length,and reservoir around the well are the important factors that affect the effect of lateral drilling horizontal well,and the high effective sand body drilling rate is an important guarantee to improve the sidetracking effect.(4)Based on the numerical simulation model of typical sidetracking horizontal well group and combined with relevant technical and economic indexes such as integrated cost of sidetracking in old wells,a comprehensive standard for optimum location selection of lateral drilling in old wells is established.The daily production of single well is less than0.2×10~4m~3/d,and the cumulative gas production is less than 1570×10~4m~3.The remaining reserves in the adjacent well area are more than 0.44×10~8m~3,and the abundance of the remaining reserves is greater than 0.54×10~8m~3/km~2.The accumulative gas reservoir thickness of the selected adjacent wells is more than 5 m,the lateral drilling interval He8_x~2,and the predicted cumulative gas production rate of the lateral drilling is more than 1770×10~4m~3.(5)According to the geological characteristics,development status and residual gas distribution 3 sidetracking horizontal wells in Su14 were selected in combination with the comprehensive criteria for location selection of sidetracking wells.Su 14-2-23,Su 14-4-33and Su 14-7-17 carried out lateral drilling horizon,azimuth and length,and predicted the development index of sidetracking.