Research On Development Performance And Well Pattern Optimization Of CBM Wells In Shizhuang South Block

Coal-bed methane(CBM)is an important unconventional energy source with huge development potential in my country.CBM in the Shizhuangnan Block in the Qinshui Basin has been commercially developed for more than ten years,but there are a large number of low-yield wells in the block,and the overall production capacity is not ideal.In order to fully understand the production rules of the production wells in the study area,the dynamic characteristics of the reservoir and the impact of well pattern deployment,this paper establishes the CBM production process based on the geology,well testing,logging,and drainage data of the CBM wells in the study area The dynamic change model of the middle reservoir,and the use of numerical simulation software to simulate the change of the existing well groups’ productivity before and after infilling,and the following understandings are obtained:(1)Based on the statistical analysis of geological parameters affecting productivity,the plane distribution map of different geological parameters and the distribution frequency map of each parameter value were drawn,and the main controlling factors of CBM well productivity in the block were quantitatively identified through gray correlation,and the results showed that they were related to productivity.The four items with the highest degree are gas content,permeability,temporary storage pressure ratio and reservoir pressure.(2)Using the reservoir pressure drop model based on the material balance equation and the permeability dynamic change model based on the effective stress effect and matrix contraction effect,the average pressure,drainage radius and permeability of the production wells with different drainage characteristics were calculated.The drainage wells with an average daily gas production greater than 1000m3/d are regarded as high-yield wells,those with an average daily gas production of 500-1000m3/d are regarded as medium-production wells,and those with an average daily gas production of less than 500m3/d are regarded as low-production wells.The drainage characteristics further divide the three types of wells,high,medium and low production,into 7 sub-categories.The calculation results show that the average reservoir pressure drop of high-yield wells is more than 70%,and the maximum drainage radius can reach 180m;the average reservoir pressure drop of low-yield wells is often less than 40%,and the drainage radius is less than 100 m.The permeability of high-production wells and type 1 middle-production wells both show an increasing trend,and the difference in up-production time affects the increase in permeability;the permeability curves of type 2 and 3 middle-production wells are all recovery types,and the permeability curves of type 2 middle-production wells There is a stable stage in the middle,there is an inflection point in the middle of the permeability curve of the 3 types of middle-production wells,that is,the rebound point;the type 1 low-production wells are fluctuating,and the second type of low-production wells are declining.The plane distribution map of the dynamic change characteristics of different types of reservoirs is drawn,which is consistent with the plane distribution map of gas production.(3)Based on Comet3 numerical simulation software,well pattern optimization and infill well simulation prediction are carried out.A single variable method was used to optimize the fracturing parameters of horizontal wells,and the effects of different horizontal section length,fracture number,conductivity and fracture length on the gas production of horizontal wells were simulated.The results show that under certain geological conditions,fracturing parameters are not as large as possible,but there are optimal values.The well spacing is simulated and optimized according to the geological conditions of different types of wells.The optimal well spacing for the first,second,and third types of areas are 250 × 300 m,225 m × 275 m,and 200 m × 250 m,respectively.The infilled horizontal wells were simulated for two vertical well groups with good geological conditions but low productivity.After infilling,the average daily production of vertical wells in the two well groups increased by 2.78 times and 2.84 times respectively compared with that before infilling.After the horizontal well is put into production,the inter-well pressure interference is high,and the pressure drop effect is obvious,which provides a reference for the later deployment of infill wells in the study area.