The pore volume compressibility(Cp)for rocks is a key parameter for evaluating the dynamic reserves of oil and gas reservoirs.However,the experimental measurement of this parameter is time-consuming,while the empirical formula method has limited applicability.Therefore,establishing a universally applicable model for pore volume compressibility for rocks is of great significance.Based on logging and well testing parameters,this study derives a generalized model that correlates Cp with porosity,rock elastic modulus,Poisson's ratio,attenuation coefficient and effective stress.The reliability of the proposed model under zero effective stress and different effective stress conditions was verified by comparing it with the Hall and Newman empirical formulas as well as experimental data from literature,within their respective applicable ranges.Finally,a sensitivity analysis on the parameters affecting the pore volume compressibility for rocks was conducted.The results indicate that:(1)The established model exhibits excellent fitting with empirical formulas and experimental data,demonstrating high reliability.(2)The porosity is the most sensitive parameter affecting Cp.Parameters required for this model are easily obtainable through conventional tests such as logging and well testing,which can significantly reduce measurement costs,boasting broad application prospects.
Under the background of dual carbon target, CCUS (carbon dioxide capture, utilization and storage) in oil and gas field has become an important carbon reduction path. At present, mature CCUS research both at home and abroad mainly focuses on enhancing the recovery rate of conventional oil and gas with CO2. Prospective exploration is being carried out for continental shale oil and gas reservoirs with stronger self-sealing ability, wider distribution and larger displacement resources. The results show that CO2 and shale reservoir have multiple actions, including water-rock mineralization reaction, competitive adsorption, crude oil dissolution, etc. The combination of multiple mechanisms can realize CO2 storage and oil and gas stimulation in shale reservoir. The research on CO2 storage efficiency and influencing factors are still in the stage of experimental simulation and numerical simulation. The influence of development method on dual-effect potential is initially considered to be related to injection temperature and pressure, fluid composition and injection mode. There are still many challenges in the storage and utilization of CO2 in shale oil and gas reservoirs. It is urgent to reveal the interaction process between CO2-water-rock-hydrocarbons in different types of shale reservoirs and the mechanism of CO2 storage, and to clarify the evolution laws of pore-fracture network expansion and deformation in shale reservoirs and the mobility of shale oil after CO2 injection. A quantitative evaluation method of CO2 long-term storage potential and shale oil limit mobility potential coupled with multi-phase and multi-field is established, which provides theoretical and technical reference for carbon storage and stimulation in shale oil and gas field.
This article takes the reservoirs of the second Member of Dengying Formation(abbreviated as Deng 2 Member)in Well Block MX 8 as research objects,and uses multiple types of data to analyze their characteristics and reservoir-controlling mechanisms,providing a theoretical basis for subsequent exploration and development.Deng 2 Member of Well Block MX 8 develops restricted platform and intra-platform mound subfacies,along with microfacies such as mound flat,mound core,mound flank and mound base.Lithologies developed in these facies include thrombolite dolomite,stromatolite dolomite,algal laminated dolomite,foam-cotton laminated dolomite,doloarenite and micrite dolomite.The reservoir space is dominated by dissolution pores and vugs,fractures are mostly high-angle structural fractures and throats are mainly sheet-like throats and necked throats.The measured porosity mainly ranges from 0.5％to 4.0％,and the permeability mainly ranges from 0.01 mD to 10.00 mD.The reservoir is mainly controlled by the following factors:(1)The microbial mounds in Deng 2 Member of the study area are mainly small mounds(rock combination type)with overall unfavorable facies belts dominated by thin interbedded layers of mound cores and mound flanks,in which dispersed thrombolite dolomite and doloarenite are mainly developed,resulting in relatively weak reservoir-forming properties.(2)The thickness of the surface karst zone is positively correlated with the reservoir thickness of the third sub-layer of the upper sub-member of Deng 2 Member,and the post-karstification paleogeomorphology controls the conservation of the karst zone;(3)Fault MX1(NE-SW trend)with extensional properties formed in the Sinian period promotes reservoir development,while the NW-SE trending strike-slip faults formed during the Indosinian-Himalayan period have the opposite effect.Karstification and Fault MX1 jointly control the reservoir development in Well Block MX8.
Low-pressure reservoirs represent a vast potential resource base.Drilling data indicate the presence of abnormal low-pressure conditions and widespread gas-bearing characteristics in Qian 1 Member of the Puguang West Syncline Area.Based on the quantitative characterization technology of formation pressure genesis of hydrocarbon generation pressure build-up and structural pressure relief models,and combined with fluid inclusion technology and basin simulation technology,this study restored the pressure evolution process of Qian 1 Member in the west syncline area of northeast Sichuan Basin by multiple methods and measures.The results show that:(1)Crude oil cracking to gas and hydrocarbon loss were the main factors causing the pressure build-up and relief in Qian 1 Member of the west syncline area,accounting for 70.73％and 51.22％respectively.In Shuangshimiao Area,the formation pressure in Shuangshimiao area rises and falls mainly due to oil generation pressurization and uplift cooling,with respective contributions of 53.7％and 39.71％.(2)The pressure evolution in Qian 1 Member has undergone four stages:the Jurassic-Early Cretaceous immature to low-mature organic matter and normal pressure stage(189-144 Ma),the mature organic matter and liquid hydrocarbon high-pressure stage(144-126 Ma),the Late Cretaceous high-mature to overmature organic matter and hyper-pressure stage(126-96 Ma),the Late Yanshanian-Himalayan tectonic pressure relief stage(96-0 Ma ago).The maximum paleopressure reached 133.88 MPa.This research enriches the theoretical study on the genesis of abnormal low pressure and provides support for hydrocarbon exploration and development.
Aiming at the problems of difficult desorption of deep coalbed methane(methane)and low productivity after fracturing in the development of deep coalbed methane in Daniudi Gasfield,experiments such as methane desorption performance testing,core damage testing and flowback fluid retention testing were carried out to investigate the effects of slickwater on the wettability,microstructure,surface charge properties of coal rocks,and methane desorption performance.The effect mechanism of slickwater on methane desorption was clarified.Meanwhile,the response surface methodology(RSM)was adopted to clarify the main controlling factors of the influence of slickwater on methane desorption performance and predict the boundary conditions of the main controlling factors.On this basis,random forest(RF)uncertainty assessment was introduced to select robust solutions insensitive to parameter perturbations,thereby increasing the credibility of the conclusions.The results show that methane desorption by slickwater is the result of competitive adsorption.After entering the coal rock matrix,slickwater occupies the methane adsorption site and promotes methane desorption.During the desorption promotion process,the salinity,contact angle with coal rock,viscosity and Zeta potential of slickwater all lead to the change of methane desorption capacity.For the performance indexes of slickwater,the main controlling factors affecting the methane desorption process are salinity and contact angle.The contact angle between slickwater and coal rock should be controlled within the range of 50°～70°,the salinity should be lower than 5×104 mg/L,which is conducive to methane desorption.The research results have important popularization significance for the development of similar coalbed methane reservoirs.
