Logging Evaluation And Application Of Rock Mechanical Properties In Conglomerate Formations

The conglomerate reservoir has great potential for exploration and development,which has abundant petroleum geological reserves and production.Compared with conventional reservoirs,conglomerate formation is characterized by poor physical property and low natural production capacity.It is generally necessary for hydraulic fracturing to transform the reservoir so as to improve the production capacity and meet the industrial requirements.In addition,a large amount of hard gravel is distributed in the conglomerate,where the formation is soft and hard interbedded with strong abrasiveness and poor drillability.This will lead to long drilling cycle and poor stability of the borehole wall.Therefore,the oil and gas drilling technology in conglomerate formation has always been a difficult problem in drilling engineering.The extension of hydraulically induced fractures,rock breaking,and borehole stability are closely related to the rock mechanical properties.Therefore,it is of great significance for the engineering application to study the rock mechanics characteristics of conglomerate formation.In view of this,the paper takes the conglomerate formation in M area as the research object.After carrying out a large number of laboratory experiments on basic physical properties and rock mechanics,basic physical parameters and mechanical parameters of the conglomerate formation are obtained,which are used to establish models of calculating rock mechanics parameters of different lithology.Logging response characteristics of different lithology are analysed.Sensitive logging curve parameters are extracted and the identification methods of lithology logging in conglomerate formation are studied by various means.On this basis,the profile of rock mechanics parameters is obtained,and then the distribution characteristics of single well rock mechanics parameters are analyzed.By predicting engineering geological parameters,caving pressure and breakdown pressure of the formation are calculated,and engineering application research such as borehole stability is carried out.The conclusions are as followed:As a whole,the physical parameters and rock mechanics parameters have wide range and strong discreteness.From the perspective of distinguishing lithology,the distribution of different lithologies parameters is narrow,indicating that the basic physical properties and rock mechanics characteristics of the same lithology have certain similarities and regularities.Therefore,on the basis of lithological classification identification,it is more reasonable to study the mechanical properties of the rock.With the decrease of gravel diameter in conglomerate formation,the rock mechanical strength decreases.In engineering applications,different lithological engineering responses have significant diversities.The hydraulically induced fractures are more likely to crack and expand in the fine conglomerate formation.There is correlation between rock mechanics parameters and physical parameters such as interval transit time and bulk density.Based on this,the establishment of models of calculating rock mechanics parameters of different lithology can effectively improve the interpretation accuracy of rock mechanics parameters in conglomerate formation.By analyzing logging response characteristics of different lithology of conglomerate formation,the lithologic identification is studied by means of crossplot method,naive Bayesian classification and principal component analysis,which can effectively identify the lithology of the target layer and basically meet the actual production needs of oilfield.Based on the field data such as logging and fracturing,the geological parameters are obtained.Combined with the rock mechanics parameters obtained by the model,the borehole stability parameters of the formation are calculated.Through the comparison and analysis of the borehole stability in drilled wells and the drilling fluid density used in the actual drilling project,models of calculating rock mechanics parameters of different lithology and the results of identification methods of lithology logging are verified.The results show that the models of rock mechanics parameter and identification methods of lithology logging constructed in this paper are reliable,which can meet the actual needs of engineering.