Research On Casing Deformation Prediction Model Of Shale Gas Field In Changning Block

During the development of shale gas in Sichuan Basin,the problem of casing deformation is prominent,which has become one of the urgent engineering problems to be solved in the development of shale gas in Sichuan Chongqing block.Based on the analysis of field casing deformation data,starting with the integration of Geology and engineering,this paper summarizes various factors affecting casing deformation,and establishes the influencing factor database of casing deformation;The weight sequence of factors affecting casing deformation is obtained by grey correlation method,and then the casing deformation prediction model in Changning block is established by using machine learning,data mining and BP neural network system theory,and the accuracy of the prediction model is verified.The main work and achievements of this paper are as follows:(1)Database construction of influencing factors of casing deformation in Changning blockBased on the comprehensive analysis of the field data of casing deformation in Changning block,it is concluded that casing deformation is the result of the joint action of geological and engineering factors,faults and natural fractures play an internal fundamental role in casing deformation,and the drilling and completion process has a direct inducing effect on casing deformation,especially the external sudden effect of fracturing construction on casing deformation;The relevant parameter database of geological and engineering factors affecting casing deformation is established.(2)Weight analysis and ranking of the influencing factors of casing deformation are completed based on the grey correlation theoryCombined with geological engineering factors,this paper uses the grey correlation theory to mine the data of shale gas casing deformation,improves the traditional grey correlation analysis method based on triangular fuzzy number,calculates the grey correlation degree of each influencing factor,completes the weight analysis and ranking of casing deformation influencing factors.Weight analysis includes 10 grey factors affecting shale gas casing deformation.The weight order is as follows: fracture orientation > fracture level > pump stop pressure > liquid volume > average construction pressure > maximum pressure / displacement > displacement > fracture length > section length > total sand volume.(3)Research on prediction model of shale gas casing deformation based on BP neural networkCombined with grey correlation analysis,the casing deformation prediction model is established based on BP neural network method.The casing deformation risk prediction is carried out for 56 shale gas wells that have been drilled in Changning block.The fitting accuracy and error accuracy of the prediction model are analyzed.The results show that the fitting accuracy of the model reaches 97.30%,the error accuracy reaches about 87%,and the model accuracy meets the application requirements.Using the actual data of 6 sample wells,the accuracy of casing deformation prediction is83.33%.(4)Predictive model example applicationThe model is used to predict the casing deformation of A1,A2 and A3 horizontal wells in Changning block.The prediction results show that the casing deformation risk coefficients of A2 and A3 wells are 0.54 and 0.63 respectively,with high deformation probability.Attention should be paid to the prevention and control of casing deformation during development.