Inter-well Interference Analysis and Well Spacing Optimization for Multi-stage Fractured Horizontal Wells of Shale Gas Reservoirs Based on Multi-information

Abstract

AbstractWell spacing is one of the key factors affecting the economic performance of shale gas reservoirs with horizontal wells. In this paper, based on the analysis of dynamic data of 180 wells in D shale gas field, we have picked the characteristic curve to identify the boundary feedback signal, which can be used to identify the inter-well interference (IWI) of different well spacing. In addition, we have innovatively formed a set of methods and processes to utilize multi-information such as micro-seismic, tracer, and adjacent well dynamic interference to analyze quantitatively the degree of IWI, which can be used to quantify the degree of IWI of different well spacing. Finally, based on the principle of keeping proper IWI and combining with the numerical simulation, the optimal well spacing is determined.Pick the characteristic curve to identify IWI. By analyzing the producing characteristics of 180 individual horizontal wells of D shale gas reservoir, we pick the double logarithmic curve of production and time as the characteristic curve that can clearly identify the boundary feedback signal. Based on this, we contrastively analyze the characteristic curve of different well spacing and find that the well spacing below 200 m reaches the boundary much earlier than the 400 m well spacing, which shows that there is serious IWI in the well spacing below 200 m.Utilize multi-information such as micro-seismic, tracer, and adjacent well dynamic interference to quantify the degree of IWI of different well spacing and determine optimal well spacing. For the micro-seismic information, we found that the micro-seismic events of each fracturing stage distributed normally along the vertical direction of horizontal well. Base on it, we standard the cumulative probability distribution curve of the micro-seismic events of each stage, and obtain the typical cumulative probability distribution curve. Then, we use the typical cumulative probability distribution curve to simulate IWI by arranging the curve according to a certain well spacing. Furthermore, we calculate the proportion of the acreage of the overlapping area of two or more curves in the middle well to the acreage of the whole individual curve to quantify the degree of IWI. For tracer information, we found that the farther away from the injection well, the less the tracer flow-back. We normalize the tracer flow-back concentration ratio (TFBCR) of injection well, and then use the TFBCR of the wells at different well spacing from the injection well to quantify the degree of the IWI. For the adjacent well dynamic interference information, we found that the smaller the well spacing, the greater the change in production caused by the shut-in of adjacent wells, the greater the difference in production between side wells and non-side wells in the same well pad. Base on it, we calculate the average production change ratio caused by shut-in of adjacent wells and the production difference ratio between side wells and non-side wells to quantify the degree of IWI. Combining the above information, the range of the degree of IWI for different well spacing can be quantitatively determined. Then, based on the principle of keeping proper IWI and combining with the numerical simulation, the optimal well spacing is determined.We applied the research achievements of this paper in D shale gas field, and found that the well spacing below 200 m had occurred serious IWI, the degree of IWI intensity of the 200 m well spacing was 11%–30%, that of the 300 m well spacing was 5%–14%. Then, based on the principle of keeping proper IWI and combining with the numerical simulation, we determined that the optimal well spacing of D shale gas field was 300 m. Consequently, we suggested expanding the well spacing of D shale gas field from 200 m to 300 m. After implementation, the individual well performance of 300 m well spacing had increased by 40% than that of 200 m well spacing and about 200 wells would be saving in the FDP.KeywordsShale gas reservoirMulti-stage fractured horizontal wellsOptimal well spacingInter-well interference