Effects Of Rock Mineral Composition On Rock Mechanical Properties

Conventional oil and gas reserves are limited,and many oil fields have reached the limit of water content,so it is urgent to develop unconventional oil and gas fields.Many unconventional oil and gas fields need stimulation measures such as fracturing to achieve good industrial productivity and effective development,and brittleness index is a key index to evaluate the fracture complexity of formation rocks after fracturing.Therefore,brittleness index has been paid more and more attention by relevant experts and scholars,and a variety of related researches have been carried out from different perspectives.The existing rock brittleness evaluation methods can be divided into elastic parameter method,rock mineral component analysis method,stress-strain curve method,impact test method,rock hardness method,etc.These evaluation methods have their own advantages and disadvantages,and there is no uniform standard.In this paper,X-ray diffractometer is used to quantitatively analyze clay minerals,quartz,feldspar,calcite and dolomite in the retrieved core from the site,and meanwhile the porosity and permeability of each core are measured.And through the triaxial stress experiment,the determination of rock stress-strain curve,the computational mechanics parameters of the elastic modulus,peak strength,peak strain,residual strength and poisson's ratio,recoverable strain,recoverable strain energy and residual strain,irreversible strain energy,total energy parameters,such as use of these mechanics parameters are calculated brittleness index,and to evaluate the brittleness index method,optimization,as real brittleness index selection optimization results.Brittleness index is divided into four grades according to the rock fracture morphology and the characteristics of the pre-peak and post-peak stress-strain curves.When the brittleness index is <0.37,the rock body shows the characteristics of toughness.When the brittleness index is 0.37 ? 0.46,the rocks show the characteristics of brittleness.When the brittleness index is 0.46 ? 0.58,the rock brittleness is better.When the brittleness index >0.58,the rock brittleness is excellent.The function relation between brittleness index and rock composition and the function relation between brittleness index and porosity and permeability were determined by SPSS.At the same time,the relationship is verified,the error meets the requirements of the site,and the relationship can be used for the field fracturing application.