【作者】 刘坤；

【导师】 孙建孟；

【作者基本信息】 中国石油大学(华东) ， 地质资源与地质工程， 2018， 博士

【摘要】 页岩气储层通常富含有机质,矿物组分和孔隙结构复杂,且多发育纳米级别的孔隙,孔隙度较小,渗透率极低,含水饱和度不易确定,含气量计算困难;同时地层各向异性和非均质性较强,层理面等结构弱面发育,钻进过程中容易发生井壁坍塌和泥浆漏失等钻井事故。A区页岩气资源丰富,勘探开发前景广阔,但也存在含气量评价困难及压裂改造效果不理想等问题。充分发挥各测井技术在页岩气储层精细评价中的应用,为本文研究的重点。即从实际储层出发,综合利用新技术测井资料以及实验分析化验结果,以页岩气的“七性”评价为总纲,重点开展高成熟度页岩储层含气性和岩石力学特性的评价,为后续页岩气储层的有效勘探开发奠定基础。本文首先根据目的层段的实际情况建立准确有效的岩石物理体积模型,分别计算有机质干酪根和无机矿物组分的含量,并进行孔隙结构评价研究。TOC含量主要分部区间为1%~5%,成熟度较高,矿物组分比较复杂,以伊利石和石英为主。孔隙类型包括有机孔和无机孔,孔隙形状主要为狭长的板状孔隙,BET法计算平均孔径为44nm,BET法计算平均比表面积为22.6m~2/g。利用岩石物理体积模型和核磁测井分别评价孔隙度,结果表明岩石物理体积模型法效果更好。考虑到孔隙中的非达西流动以及吸附作用会使视渗透率增加,本文在克努森数进行孔隙流态分析的基础上,综合考虑滑脱、扩散作用以及吸附作用的耦合,得到视渗透率校正系数,进而对绝对渗透率进行相应的校正。从声波的角度出发,根据BISQ模型研究影响纵横波速比的相关因素,结果表明在特征喷射流长度一致的情况下,主要影响因素为含水饱和度和孔隙度,并据此构建了含水饱和度的计算新模型,该方法不受有机质和导电重矿物的影响,克服了电阻率法计算含水饱和度的不足,提高了含水饱和度计算精度。开展等温吸附和声波联测实验,研究不同孔隙压力条件下,声波幅度衰减与对应的游离气和吸附气含量之间的关系。结果表明声波幅度衰减系数和孔隙度越大,游离吸附比越大,进而构建出游离吸附比计算新模型,计算结果与基于等温吸附和孔隙体积计算的游离吸附比一致,实现了游离吸附比的准确有效评价,克服了原有方法受控于评价参数复杂繁多的弊端,使得含气量的计算方法更加简单灵活。在阵列声波测井资料的基础上,对该区页岩地层分别进行2D和3D各向异性评价,结果表明页岩地层2D各向异性弱,3D各向异性强,验证了页岩地层为典型的TIV介质。系统的介绍了弹性参数以及强度参数的计算方法,并根据等效介质模型估算固体混合物的剪切模量,在此基础上计算了Biot系数,计算结果与渗透率计算的静态Biot系数结果基本一致,提供了一种基于矿物组分和声波测井估算Biot系数的新思路。在进行孔隙压力预测时,依次对纵波时差利用岩石物理体积模型进行有机质校正以及根据经验公式进行含气性的校正,使得建立压实趋势线的泥岩小层具有相同的标准,提高了孔隙压力的预测精度,并与实际的钻井结果相一致。利用小型压裂测试约束最小水平地应力,在此基础上利用应力多边形法和井壁崩落约束最大水平地应力,验证了原地应力计算结果的准确性。系统分析原地应力、基质强度、弱面强度和弱面产状对泥浆安全密度的影响,建立了多弱面条件下任意井斜(0~90~o)和方位(0~360~o)下的井壁稳定性评价流程,准确评价泥浆安全密度窗范围,为井眼轨迹优化以及钻井过程的顺利进行提供了理论支撑。利用弹性参数对矿物组分进行校正以突出不同矿物组分间脆性的差异,进而得到脆性指数计算新模型,相较单独的声波法和矿物组分法,新模型提高了脆性指数对可压性层段的指示准确度;综合利用单轴抗压强度、新脆性指数和断裂韧性构建了可压性的评价新指标,将地层的可压性分为三类,评价结果与实际测试结果一致,为该区页岩气储层的压裂施工提供了相应的技术支持。更多还原

【Abstract】 Shale gas reservoirs usually have a number of organic matters,more complicated mineral components and pore structures,more nanoscale pores,low porosity and permeability.The water saturation and gas content are difficult to calculate.At the same time,the anisotropy and heterogeneity are strong.Due to the presence of bedding and other structural weakness planes,borehole collapse,mud loss,and other drilling accidents are easy to occur during drilling.The A area has abundant shale gas reservoirs,and has good potential for prospecting and exploitation.However,there are also problems including gas content evaluation and poor production performance after hydraulic fracturing.Fully utilizing a variety of logging evaluation techniques in shale gas reservoirs is the focus of this study.From the actual reservoir,comprehensive utilization of the logging data of new technologies and experimental results based on seven properties evaluation,gas-bearing and rock mechanical properties are well studied.This research can lay the foundation for the effective exploration and development of shale gas reservoirs.In this paper,an accurate and effective petrophysical volumetric model is established based on the actual condition of interest interval,and the content of organic and inorganic matters are calculated separately.Then,the pore structure is studied.The TOC content ranges from 1%to 5%with high maturity.And the mineral components are very complex dominated by illite and quartz.The pore type includes organic pores and in-organic pores.The pore shape is mainly long and narrow,the BET average pore diameter is 44nm,and the BET average specific surface area is 22.6m~2/g.The porosity is evaluated by the petrophysical volumetric model and NMR log,and the results show that the petrophysical volumetric model method is better.The non-Darcy flow and adsorption effect will increase the apparent permeability.Flow regime is analysised by Knudsen number,and the apparent permeability coefficients are calculated taking into the slip-flow and adsorption effect.Then,the absolute permeability can be corrected.From the perspective of sonic logging,based on BISQ model,the correlation factors affecting Vp-to-Vs ratio are studied,and the results show that the main influencing factors are water saturation and porosity under the condition that the squirt-flow lengths are the same.Then,the new water saturation calculation model is eatabilished.The new model is not affected by organic matter and conductive heavy minerals,and improves the calculation accuracy of water saturation compared with resistivity method.Conducting the isothermal adsorption and acoustic amplitude joint experiment.Under different pore pressures,the relationship between the amplitude attenuation coefficient and the gas content is studied.And the results show that the free-to-adsorbed ratio increases with the increase of amplitude attenuation coefficient and porosity.Then,a new model of free-to-adsorbed ratio is established.The practical applications are found to be in good agreement with the results of the traditional methods,which provides a flexible and effective method to evaluate gas content using less parameters.Based on the array sonic logging data,2D anisotropy and 3D anisotropy are characterized in shale gas reservoirs.And the results show that 2D anisotropy is weaker,however,3D anisotropy is stronger showing that the shale formation is TIV media.Then,the calculation methods of elastic parameters and strength parameters are systematically interpreted.The Biot coefficient is estimated with the shear modulus of the solid mixture,and the results are found to be in good agreement with the static Biot coefficients calculated by permeability,providing a new method for calculting Biot coefficient using mineral compositions and wave velocity.During the prediction of pore pressure,the compression wave slowness is corrected for organic matters according to the petrophysical volumetric model,and the gas-bearing correction is carried out based on the empirical formula.Then,the mudstone layers have the same criteria for estabilishing normal compaction trend line and the estimation accuracy of pore pressure is improved.Small fracturing tests is used to constrain the minimum horizontal stress.Stress polygon method and borehole collapse images are used to constrain the maximun horizontal stress,showing that the calcualtion of in-situ stress is reliable.The influence of in-situ stress,intact rock strength,weak plane strength,and weak plane occurrence on safe drilling mud density are analyzed systematically under arbitrary azimuth(0~360~o)and inclination(0~90~o).Then,the evaluation process of wellbore stability is established,which provides a theoretical support for the wellbore trajectory optimization and drilling process successfully.The brittleness difference between different mineral components is highlighted using the elastic parameters to correct the mineral components.Then a new brittleness calculation model is established.Compared with the acoustic method and the mineral constituent method,the new model improves the brittleness accuracy.Based on the uniaxial compressive strength,new brittleness and fracture toughness,a new fracability index is established and the formation fracability is divided into three categories.The evaluation results are in good agreement with the actual test results,and the new fracability index provides the corresponding technical support for the development of shale gas reservoirs.更多还原