Numerical Simulation Study On Acid Fracturing Of Low Geophysical Segment To SAGD Of Dual Horizontal Wells

With the rising demand for oil resources and the reduction of conventional oil and gas resources,the country is paying more and more attention to the development and utilization of super heavy oil.As a frontier technology for the exploitation of super heavy oil,steam assisted gravity drainage(SAGD)heats the cold oil zone through the continuous expansion of the steam chamber,and the crude oil is discharged under steam displacement and gravity,which has a high recovery rate.Therefore,research on SAGD technology is of great significance for the exploitation of super heavy oil reservoirs.The object of this study is a block where low geophysical segments are of Liaohe heavy oil reservoir,which was initially developed by steam stimulation and then SAGD.However,due to low geophysical segments of the reservoir,the SAGD steam chamber cannot be extended vertically and the oil above them is not used to a large extent.Therefore,it is proposed to transform low geophysical segments of the reservoir by acid fracturing technology.In view of the above problems,this paper studied the characteristics of the low geophysical segments of the target block,found the method to identify the low geophysical segment,and then reclassified reasonably the low geophysical segment types for this block according to the physical property,thickness,breakthrough time and other indicators of the low geophysical segment.Taking the SAGD of double horizontal wells as an example,according to the geological characteristics,seismic data and drilling data of the target block,the 3D geological model is established,with a reserve fitting error of 1.26%.Then according to the geological model result,the numerical model of this block is established with CMG software and the small layer where the low geophysical segment is located is encrypted in the model,and the history matching of the whole area and single well is completed,and the influence of low geophysical segment for remaining oil is analyzed.Through the reservoir numerical simulation software to simulate the low-physical segment acid pressure transformation,combined with the on-site construction situation,the control variable method is used to optimize the number of cracks,crack half length,slit width and acid dosage.Then orthogonal test design method was used to study the acid pressure parameters.The results of the analysis were analyzed by visual analysis and analysis of variance.The number of cracks,the length of the crack,the width of the slit and theamount of acid used in the primary and secondary stages of the acid pressure are analyzed.Then the effect of acid pressure transformation in low geophysical segment is evaluated from the shape of steam cavity,sweep coefficient and production index.Some conclusions are obtained to guide the design of the low geophysical section of the target block,and provide scientific basis for the reasonable transformation of the low geophysical section of the target block by acid fracturing.