Study on Tertiary Infilling Adjustment Optimized Well Spacing at Super High Water Cut Stage

Abstract

Abstract. In view of the features of the remaining oil after a period of production since secondary infilling adjustment of water flooding development oil field, that is, low quality, uneven planar distribution and high vertical dispersal, study on tertiary infilling adjustment optimized well spacing has been carried out in the East of North 3 Block of North Sartu Development Area. The study has solved the problems of reasonable well spacing density, injector-producer distance, injection-production system, how to locate wells near old injector array, and how to adjust and integrate with the original well pattern, with the tertiary recovery well pattern and with the injection-production system. The overall strategy and optimized well spacing method for tertiary infilling adjustment have been brought forward consisting of reasonable well location region division →balanced well spacing →well by well scanning →local adjustment →step by step implementation. The study has a wide guidance for the tertiary infilling adjustment of other blocks to find practical, feasible and effective approaches. East of North 3 Block Development OverviewEast of North 3 Block in North Sartu Development Area is located in the north pure oil area of Sartu Oilfield in Daqing placanticline with an oil bearing area of 20.2km2. The block was brought into development in 1965 as major reservoirs in Sartu and Putaohua oil-field [1] . Since then two times of infilling adjustment had been conducted aiming at PⅡ, Gao Middle, low permeability layers and Sartu thin and poor reservoirs. 250×300m inverted nine spots area injection pattern is adopted without exception. After secondary infilling, the well spacing density reached 30.25 wells/ km 2 . According to the refined geologic anatomy result, the remaining adjustable sandstone thickness after secondary infilling adjustment in East of North 3 Block is predicted as 12.44m and the effective thickness is 1.88 m [1] . Tertiary infilling adjustment has certainly material base, but uneven the remaining oil planar distribution and vertical high resolution have determined to the hardness of production potential development. Therefore, the approach should be started from technical and economical indexes to optimize well spacing with a possible better adjustment effect. Study on Tertiary Infilling Adjustment Optimized Well Spacing in East of Injection-Production System ScreeningNumerical simulation is applied to compare the development effects of five-spot pattern, four-spot pattern, and inverted nine spots injection-production systems in the thin and poor oil layers and surface layers in East of North 3 Block. The result shows that the average control degree of water flooding of five-spot area well pattern is 8-10% high than other well patterns. At the same water cut, the recovery degree is higher than other injectionproduction systems. Therefore, the injection-production system of tertiary infilling adjustment in East of North 3 Block should select five spots pattern [2][3][4][5] . The test well data statist...