摘要：Affected by multiple factors such as magma composition,eruption method,surrounding environment of volcanic crater,diagenesis,and later transformation,volcanic rocks have the characteristics of multiple rock types,complex lithology,rapid changes in lithofacies,and large differences in physical properties and pore structures.There are very few studies on the evaluation of volcanic rock mechanical properties and in-situ stress.In this paper,taking the Permian volcanic rock oil and gas reservoir in Xinjiang Oilfield as an example,we have conducted a systematic study on the rock mechanical properties of volcanic rock and the in-situ stress logging evaluation method,based on clarifying the type of volcanic rock.The study found that the volcanic rocks in the study area include volcanic lava,pyroclastic lava,pyroclastic and plutonic intrusive rocks.The porosity of volcanic rock reservoirs is mainly distributed between 0.1% and 15.9%,with an average of 3.3%.The permeability is mainly distributed from O.OlmD to 597mD,with an average value of 7.31mD.According to the rock mechanics experiment and logging interpretation,the dynamic and static mechanical parameter conversion model of volcanic rock is established.At the same time,the Terzaghi model,Newberry model,Huang model and Mohr-Coulomb model are selected to perform logging evaluation of the in-situ stress of the target formation.The applicability of the horizontal in-situ stress model is analyzed,and it is found that the trend of the isotropic model curve and the pore pressure curve are basically the same.This shows that the pore pressure is greatly affected,and it is difficult to reflect the true horizontal stress change trend of the formation.However,the curve of the Mohr-Coulomb-based in-situ stress model changes drastically,and it is greatly affected by the larger friction angle,and the curve is prone to distortion.Therefore,the Huang's model was finally selected to evaluate the horizontal ground stress.The average absolute error between the rock fracture pressure calculated in this study and the actual fracture pressure measured during fracturing construction is 1.65 MPa,and the average relative error is 4%,indicating that the log calculation results are reliable.
关键词：Volcanic rock;rock mechanical properties;in-situ stress;well logging evaluation;Huang's model
