基于全缝长压裂模拟技术的致密储层压裂改造效果定量表征

在考虑压裂液滤失的压裂缝形成机制的基础上,利用石油工程地质一体化的全缝长压裂数值模拟技术,结合储层地质分析及精细油气藏三维建模,对松辽盆地白垩统泉头组扶余油层开展水力压裂的目的储层段压裂改造效果定量表征研究。结果表明研究区储层微观裂缝较为发育,黏土矿物含量较高,自生石英较为发育,对岩石的力学性质影响较大,将不可避免地影响到水力裂缝的张开及导流能力的非均质性;各小层压裂改造效果的“有效导流范围”均可进一步细分为四级导流区,对原油开采将起到不同程度的促进作用;提出的“单砂体产液量极限值”及“微地层单元产液量极限值”概念及计算方法,可为评估单砂体内部产能贡献提供借鉴,有利于开展单砂体“靶向”改造。

致密砂岩储层敏感性评价及影响因素分析——以鄂尔多斯盆地盐池地区长8储层为例

以鄂尔多斯盆地盐池地区长8储层为例,利用薄片鉴定、X射线衍射、高压压汞和岩芯流体驱替实验等手段,对储层的敏感性开展定量评价,并深入剖析其影响因素。结果表明,鄂尔多斯盆地盐池地区长8致密砂岩储层的敏感性主要表现为中等偏强水敏、弱-中等偏弱酸敏、弱-中等偏弱碱敏和弱盐敏特征。储层的敏感性特征受黏土矿物成分、岩石矿物学特征、孔隙结构和物性影响,其中黏土矿物的含量和组成是主要影响因素,实际开发过程中应予以高度重视。研究结论可为致密砂岩油藏开发中后期提高采收率提供重要的科学依据。

水力压裂缝动态非对称延伸过程数值模拟

从"人工油气藏开发"的角度,采用全缝长压裂缝模拟技术,结合储层精细地质建模技术对低渗透储层水力压裂过程中形成的原位储层-支撑剂复合体的动态延伸过程及其变化特征进行探索,提出以水力压裂缝动态非对称指数来表征水力压裂缝动态非对称延伸特征,构建原位储层-支撑剂复合体的评价参数,探索水力压裂缝动态非对称指数在常规测井曲线中的响应特征,并据此建立基于常规测井曲线的水力压裂缝动态非对称延伸特征的方法。研究结果表明,全缝长压裂缝模拟技术优于仅基于常规测井数据的半缝长非对称压裂缝模拟技术,便于开展储层非均质性研究。水力压裂缝动态非对称指数可以反映水力压裂缝在某一压裂时长的非对称延伸规模水平,结合储层物性与目前开发动态可为实现储层的充分动用提供指导。水力压裂缝动态非对称延伸特征剖析是提高采收率的重要研究方向。

围压-孔压改变条件下致密砂岩及泥页岩泊松比变化特征及机制

在围压(外压)或孔压(内压)发生变化的条件下,致密砂岩及泥页岩泊松比的变化特征及机制仍有待厘清。本研究从Terzaghi有效应力理论和国内学者提出的新有效应力概念出发,基于松辽盆地高台子组致密砂岩、青山口组泥页岩三向动、静态泊松比测定结果,剖析了两类岩石泊松比的变化特征及机制。岩石样品三向泊松比变化曲线的分布呈现显著的各向异性,这将对压裂缝的延展规律产生一定的影响;就“有效应力”概念厘定的科学性而言,“Terzaghi有效应力”适用于裂缝较为发育的储层,而“新有效应力”适用于孔隙度较大且分布较为均匀的泥页岩。结论将为致密油气的有效开发提供较为重要的理论依据。

页岩储层应力敏感性定量评价:思路及应用

应力敏感性定量评价是页岩油气勘探开发中公认的关键工程难题之一,然而变应力条件下页岩孔缝尺寸及渗透率下降规律等问题至今尚无定论,亟待深入探索.本文从Griffith经典弹性力学解出发,在充分刻画非均质页岩孔隙和微裂缝的基础上,通过建立横截面为椭圆的柱体管束模型,推导得到应力作用下岩石渗透率保持水平的计算公式,基于此给出适宜于非均质页岩油储层的应力敏感性评价思路及覆压渗透率计算公式,最后在中国西部和中部典型页岩油储层中开展了工程应用.研究显示:(1)相同应力状态下,页岩油储层应力敏感程度由储渗空间初始长短轴比值、杨氏模量及泊松比共同控制;(2)裂缝型页岩由于发育长短轴比值较高,其应力敏感程度略高于裂缝发育程度较低的基质型页岩,且杨氏模量越小,两类页岩应力敏感程度差异性越大;(3)在40 MPa的有效应力作用下,裂缝型和基质型页岩油储层渗透率损耗程度最高值分别不足10%和8%,证明页岩应力敏感程度总体较低.应力敏感性对于页岩油原位储量及实际产能的影响程度亟需在工程实际中予以重新审视.研究成果将为页岩油储量的精确评估和采收率的高效提升提供新的理论与实践依据.

Imaging-Based Characterization of Perthite in the Upper Triassic Yanchang Formation Tight Sandstone of the Ordos Basin,China

This work investigated the element distribution of perthite from the Upper Triassic Yanchang Formation tight sandstone in the Ordos Basin of northern China by field emission scanning electron microscopy(FE-SEM) and energy dispersive spectrometer(EDS). FE-SEM results indicate significant differences in the morphology of Na-rich feldspar when K-rich feldspar is the main component of the perthite. EDS results show that different types of perthite have clearly defined differences on different element indexes. Additionally, indexes such as average-weight-K(K-rich)/Na(Na-rich), maximumweight-K(Na-rich)/Na(Na-rich) and average-atomic-K(K-rich)/Na(Na-rich) might be the most effective ones to identify perthite types. Perthite is divided into six main types, i.e., perthite with thick parallel stripe distribution, with thin parallel stripe distribution, with lumpy stripe distribution, with dendritic stripe distribution, with encircling stripe distribution, and with mixed stripe distribution.

Anisotropic Rock Poroelasticity Evolution in Ultra-low Permeability Sandstones under Pore Pressure,Confining Pressure,and Temperature:Experiments with Biot's Coefficient

This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure,confining pressure,and temperature.Several groups of experiments examining Biot's coefficient under different conditions were carried out.Results showed that Biot's coefficient decreased with increased pore pressure,and the variation trend is linear,but the decreasing rate is variable between materials.Biot's coefficient increased with increased confining pressure;the variation trend is linear,but the increasing rate varies by material as well.Generally,Biot's coefficient remains stable with increased temperature.Lithology,clay mineral content,particle arrangement,and pore arrangement showed impacts on Biot's coefficient.For strong hydrophilic clay minerals,expansion in water could result in a strong surface adsorption reaction,which could result in an increased fluid bulk modulus and higher Biot's coefficient.For skeleton minerals with strong lipophilicity,such as quartz and feldspar,increased oil saturation will also result in an adsorption reaction,leading to increased fluid bulk modulus and a higher Biot's coefficient.The study's conclusions provide evidence of poroelasticity evolution of ultra-low permeability and help the enhancing oil recovery(EOR)process.

Rapid Determination of Complete Distribution of Pore and Throat in Tight Oil Sandstone of Triassic Yanchang Formation in Ordos Basin, China

This study aimed to investigate the complete distribution of reservoir space in tight oil sandstone combining casting slices, field emission scanning electron microscopy(FE-SEM), the pore-throat theory model, high-resolution image processing, mathematical statistics, and other technical means. Results of reservoir samples from the Xin’anbian area of Ordos Basin showed that the total pore radius curve of the tight oil sandstone reservoir exhibited a multi-peak distribution, and the peaks appeared to be more focused on the ends of the range. This proved that pores with a radius of 1–50,000 nm provided the most significant storage space for tight oil, indicating that special attention should be paid to this range of the pore size distribution. Meanwhile, the complete throat radius curve of the tight oil sandstone reservoir exhibited a multipeak distribution. However, the peak values were distributed throughout the scales. This confirmed that the throat radius in the tight oil sandstone reservoir was not only in the range of hundreds of nanometers but was also widely distributed in the scale approximately equal to the pore size. The new rapid determination method could provide a precise theoretical basis for the comprehensive evaluation, exploration, and development of a tight oil sandstone reservoir.

Pore Structure Characterization of Clay Minerals in the Lower Karamay Formation Conglomerate Reservoir in the Junggar Basin and its Impact on Hydrocarbon Storage and Seepage

The micro-nano pore structure of conglomerate in the Lower Karamay Formation of the Xinjiang Oilfield,Junggar Basin,northern China is characterized to predict its impact on fluid reserves and seepage.Authigenic clay minerals are mainly kaolinite(67%),followed by an illite/smectite mixed layer(18%),illite(10%),and chlorite(5%).For kaolinite,pore throats between 0–200 nm are dominant,accounting for 90%of the total pore throats.For illite/smectite mixed layer,pore throats also between 0–200 nm account for nearly 80%,while pore throats between 200-500 nm only account for 15%.For illite,pore throats below 100 nm account for about 80%,while pore throats in the range of 100–500 nm only account for 20%.For chlorite,most throats are below 200 nm.The pore roundness of illite is the highest,while the pore roundness of chlorite is relatively lower.The lower limits of the dynamic and static pore throat radii are 42.128 nm and 72.42 nm,respectively.The theoretical contribution rates of the illite/smectite mixed layer,kaolinite,illite and chlorite to storage/seepage are 60%/45.86%,52.72%/38.18%,37.07%/28.78%and 32.97%/26.3%,respectively.Therefore,the contribution rates of clay minerals in the study area are as follows:illite/smectite mixed layer,kaolinite,illite and chlorite.

Petroleum Geological Map of Igneous Rocks in the Basins of China and Adjacent Areas

There are much information such as fault structure,stratigraphic distribution and filling features,basal features and igneous rock distribution which are concealed inside the basins of China and adjacent regions.These

用“伞式解构”方法剖析致密储层微观各向异性

致密油气储层作为非常规油气储层的重要类型,具有孔隙尺度小,微观非均质性强等显著特征.目前在大幅提高资源动用率方面仍面临重大理论挑战,探索潜力广阔.本研究利用"伞式解构"方法定量解析了中国鄂尔多斯盆地陆相致密砂岩储层孔隙和矿物的微观各向异性特征.实例研究显示,八向伞式切片微观孔喉发育存在显著的微观各向异性,各向填隙物发育特征差异明显,随着取样角度的变化,呈现连续非稳态分布.八向伞式切片分形维数是孔隙率、渗透率和孔喉发育概率的良好表征.研究可为揭示致密储层储渗机理及"甜点"分布规律,指导致密油气有效开发提供重要的理论支撑与实践依据.

长石粒内孔流体充注规律及分形特征：以鄂尔多斯盆地延长组致密砂岩储层为例

鄂尔多斯盆地延长组致密砂岩储层长石含量较高且脆性破裂发育广泛,目前对该类储层长石粒内孔流体充注规律及分形特征等了解仍然十分匮乏.综合铸体薄片、场发射扫描电镜、图像处理、分形维数计算等手段,提出"粒内充注"概念并对延长组储层长石粒内孔开展了微观充注过程定量模拟,指出长石粒内孔相对于粒间孔的特殊性.从时间上将粒内充注过程划分为前期非稳态充注和后期稳态充注两大阶段,转折点为充注关键时刻.依据充注速率值分布特点,将长石粒内孔某一时刻发生充注的所有空间位置划分为高速充注区、中速充注区、低速充注区三大充注区域,并建立了粒内充注波及系数幂函数变化曲线,厘清了流动轨迹分形维数的物理意义.研究成果可为鄂尔多斯盆地延长组储层油气成藏过程恢复提供较为重要的启示.