Research On Comprehensive Sweet Spot Evaluation Of Tight Oil Reservoirs In Block X

As China’s oil and gas exploration and development technology becomes more mature,unconventional tight sandstone oil and gas resources show great development potential.At present,horizontal well volumetric fracturing combined with elastic depletion mode is widely used to develop unconventional tight oil and gas resources at home and abroad.The evaluation of tight oil reservoir sweet spot is one of the key technologies to realize the efficient development of tight oil.There are many kinds of evaluation methods for tight oil reservoir sweet spots,but their applicability and accuracy are limited.Therefore,it is urgent to establish an integrated sweet spot identification method for tight reservoir,which can comprehensively consider rock mechanical properties,rock physical logging response characteristics,reservoir physical property parameters,reservoir oil saturation and other influencing factors.In this paper,the tight oil reservoir in Block X is taken as the research object.In view of its characteristics of low porosity,low permeability and complex pore structure,laboratory tests of core overburden pore permeability,triaxial stress and rock acoustic and electric tests are carried out.The pore and permeability parameters of core under effective overburden pressure were measured,the porosity and permeability loss caused by stress sensitivity of reservoir were analyzed,and the relationship between rock mechanical parameters,shear wave and p-wave velocity and rock resistivity with water saturation was determined.The experimental results show that the target reservoir in block X has strong stress sensitivity,elastic modulus of 22.09 GPa,poisson’s ratio of 0.219 and compressive strength of about 97.0MPa.Based on laboratory test data and logging data,the porosity prediction section,permeability prediction section and rock brittleness index prediction section of the target reservoir in block X are established,and the oil saturation interpretation model of the target reservoir is established by using Archie formula.Based on the principle of cluster analysis,the classification criteria of reservoir logging lithofacies are divided into five categories in engineering sweet spot and four categories in reservoir quality sweet spot.Combined with reservoir quality sweet spot and engineering sweet spot classification and classification evaluation standard,the comprehensive sweet spot classification and classification evaluation standard of target reservoir in block X is established.Based on the comprehensive sweet spot classification and grading evaluation results,a quantitative analysis method is established for the influence of different logging rocks on oil well production in tight reservoirs.Based on the oil test data of six development wells,the fluid production intensity of each type of lithofacies in different comprehensive desserts was obtained.According to the liquid production intensity corresponding to different types of rock,the production prediction model of target block is established,which lays a foundation for the comprehensive sweet spot classification and grading evaluation of tight oil reservoir in block X.