Study On The Main Controlling Factors Of Waterflood Huff And Puff With The Horizontal Well In Tight Oil Reservoir

Tight oil resource is abundant and widely distributed with extremely important development value.However,due to the tight lithology,complex pore structure and the development of natural fractures,it is very difficult to develop tight reservoirs by conventional water injection.Taking the Chang 6 reservoir in the HL study area of Yanchang oilfield as an example,the reservoir characteristics of tight reservoirs were studied and the imbibition law of fractured tight reservoirs was clearly defined by the experiment of static imbibition,dynamic imbibition and waterflood huff-puff in this paper.Comprehensively considering the flow law and pressure change of fluid during waterflooding,well closing period and oil recovery,the capacity model of waterflood huff and puff in horizontal wells with volume hydraulic fracturing was built and the mathematical model was solved by the finite difference method.Comparing with the results of numerical simulation and the experimental results of water injection and puff,the correctness of the prediction model for water injection and puff capacity was verified.According to the actual geologic data of HL study area in Yanchang Oilfield and the existing well logging and micro-fracture detection data of horizontal wells with volumetric hydraulic fracturing,a conceptual model,reflecting the reservoir characteristics,was established.And the engineering factors affecting the waterflooding huff-puff were analyzed by the way of numerical simulation.Firstly,the single factor analysis was used to simulate and optimize the single period water injection rate,water injection speed,well shut-in time and liquid production rate.Then,the orthogonal test design method was used to carry out the multi-factor simulation according to the single factor optimization results.Finally,the influnce degree of four factors on the oil production effect of waterflood huff-puff are as follows:periodic water injection rate>liquid production rate>well shut-in time>water injection speed.Meanwhile,the best combination of injection and production parameters is obtained,which is that periodic water injection rate is 3300m~3,water injection speed is 80 m~3/d,well shut-in time is 25 days and liquid production rate is 12.5 m~3/d,and it provides an important theoretical basis for the field test of waterflood huff-puff in the horizontal well of the study area.