Logging Evaluation of the Ordovician Carbonate Reservoir Beds in the Lungudong Region,Tarim Basin

In recent years, great progress has been made constantly in oil and gas exploration in the Lungudong region of the Tarim Basin. However, progress has been slow in the evaluation of its main oil-producing horizons -- the Ordovician carbonate reservoir beds. Based on previous researches and on the various data such as drilling, geology and oil test, in combination with the interpretation of each single-well imaging and conventional logging data, and through analysis and comparison, the identification methods in imaging and conventional logging for four types of carbonate reservoir beds in this region are summarized in this paper. Calculation formulas for four reservoir bed parameters, i. e. shale content, porosity, permeability and oil saturation in this region are proposed; and reservoir beds in this region are divided into three levels （Ⅰ, Ⅱ and Ⅲ） by combining oil test data and logging data, The lower limits of the effective porosity of reservoir beds and the fracture porosity of effective reservoir beds are determined as 1.8% and 0.04%, respectively. The physical property parameters are calculated by conventional logging curves, and the most advantageous areas for reservoir development are predicted comprehensively. On the plane, the high-value zones of reservoir bed parameters are mainly concentrated in the N-S-trending strike-slip fault, the Sangtamu fault horst zone and near the LG38 well area; vertically, the reservoir bed parameters of the Yijianfang Formation are better than those of the Yingshan and Lianglitage formations.

Research on reservoir bed heterogeneity,interlayers and seal layers and controlling factors of 2+3 sands of upper second member,Shahejie Formation,in the west of the Pucheng Oilfield

Terminal fans have formed the sedimentary system of the 2＋3 sands of the upper second member, Shahejie formation in the west of the Pucheng Oilfield, Bohai Bay Basin, East China. Based on well logging data and physical properties of the reservoir beds, the 2＋3 sands were divided into 16 sublayers. The heterogeneity of reservoir beds and distribution of interlayers and seal layers in the 2＋3 sands were investigated. The intra-layer heterogeneity and inter-layer heterogeneity primarily belong to the severely heterogeneous classification. The spatial differentiation of sedimentary microfacies resulted in a change of reservoir bed heterogeneity, strong in the middle and southern parts, weak in the northern part. Spatial distribution of interlayers and seal layers is dominated by sedimentary microfacies, and they are thick in north-eastern and middle parts, thin in the south-western part.

Sedimentary Micro-facies and Macro Heterogeneity of Reservoir Beds in the Third Member of the Qingshankou Formation,Qian'an Area,Songliao Basin

An analysis of drill cores and well logs shows that the main micro-facies of the third member sand bodies of the Qingshankou Formation in Qian＇an are subaqueous distributary channel facies, sheet sand facies and subaqueous fan facies （olistostrome）. Maps showing the distribution of these micro-facies together with inter-channel bay and prodelta mocro-facies are presented for different time-slices （lower, middle and upper parts of the Qingshankou Formation）. These maps reveal the instability and change of sediment transport in the Baokang sedimentary system during the depositional period. Sediment transport was from the west in the early stage, from the south in the middle stage and from the northwest in the late stage. Values of thickness, porosity and permeability of the sand bodies in the third member of the Qingshankou Formation show that they have low to medium porosity and low permeability, and are characterized by serious reservoir heterogeneity. The joints between micro-facies and subaqueous fan micro-facies are characterized by the highest heterogeneity, the sheet sand and distal sand bar subfacies come next, and the heterogeneity of the subaqueous distributary channel sand bodies is relatively weak.

Application of Spectral Decomposition to Detection of Fracture-Cavity Carbonate Reservoir Beds in the Tahe OUfield,Tarim Basin,NW China

Ordovician fracture-cavity carbonate reservoir beds are the major type of producing formations in the Tahe oilfield, Tarim Basin. The seismic responses of these beds clearly changes depending on the different distance of the fracture-cavity reservoir bed from the top of the section. The seismic reflection becomes weak or is absent when the fracture-cavity reservoir beds are less than 20 ms below the top Ordovician. The effect on top Ordovician reflection became weaker with deeper burial of fracture-cavity reservoir beds but the developed deep fracture-cavity reservoir beds caused stronger reflection in the interior of the Ordovician. This interior reflection can be divided into strong long-axis, irregular and bead string reflections, and was present 80 ms below the top Ordovician. Aimed at understanding reflection characteristics, the spectral decomposition technique, which uses frequency to ＂tune-in＂ bed thickness, was used to predict Ordovician fracture-cavity carbonate formations in the Tahe oilfield. Through finely adjusting the processing parameters of spectral decomposition, it was found that the slice at 30 Hz of the tuned data cube can best represent reservoir bed development. Two large N-S-trending strong reflection belts in the mid-western part of the study area along wells TK440- TK427-TK417B and in the eastern part along wells TK404-TK409 were observed distinctly on the 30 Hz slice and 4-D time-frequency data cube carving. A small N-S trending reflection belt in the southern part along wells T403-TK446B was also clearly identified. The predicted reservoir bed development area coincides with the fracture-cavities connection area confirmed by drilling pressure testing results. Deep karst cavities occur basically in three reservoir bed-development belts identified by the Ordovician interior strong reflection. Spectral decomposition proved to be a useful technique in identifying fracture-cavity reservoir beds.

Influence of Bedding and Mineral Composition on Mechanical Properties and Its Implication for Hydraulic Fracturing of Shale Oil Reservoirs

The premise of hydraulic fracturing is to have an accurate and detailed understanding of the rock mechanical properties and fracture propagation law of shale reservoirs. In this paper,a comprehensive evaluation of the mechanical properties of the shale oil reservoir in the south of Songliao Basin is carried out. Based on the experiments and the in-situ stress analysis, the fracture propagation law of three types of shale reservoirs is obtained,and the suggestions for fracturing are put forward. The results have shown that the fracture propagation of pure shale and low mature reservoir is easy to open along the bedding plane under compression loading,which is greatly influenced by the bedding. Sand-bearing shale is slightly better,the fractures of which are not easy to open along the bedding plane. The mechanical experimental results show that all the samples have the characteristics of low compressive strength,low Young’s modulus and strong anisotropy,indicating that the shale oil reservoir is certain plastic,which is related to its high clay mineral content and controlled by the bedding development. Compared with pure shale and low mature shale,the sandbearing shale has less clay content and less developed bedding,which maybe the main reason for its slightly better brittleness. Overall,the expansion of hydraulic fracture is controlled by in-situ stress and bedding. Because of the development of bedding,it is easy to form horizontal fractures. Thus it is not suitable for horizontal well fracturing.Because of the high content of clay minerals,the applicability of conventional slick hydraulic fracturing fluid is poor. It is suggested to use vertical well or directional well to carry out volume fracturing. In this way,the effect of bedding can be effectively used to open and connect the bedding and form a larger fracture network.

The Silurian Reservoir Bed-Differentiated Asphalts in Tarim Basin and Modeling Experiments on Their Origin

There is a type of asphalt that originated from differentiation from reservoir bed (named reservoir bed\|differentiated asphalt) in the Silurian asphaltic sandstones of the Tarim Basin. These asphalts are the result of second\|time charging of hydrocarbons into the Silurian reservoir, which were derived from Lower Paleozoic source rocks. Asphalt was differentiated from the reservoir bed in the hydrocarbon gathering area of secondary migration. The differentiation is caused by changes in reservoir physical properties when pearl or chain hydrocarbons migrating through and gathering in the reservoir bed, and light components are lost and heavy ones are involved in the formation of asphalt or heavy oil. There are two kinds of occurrence of these asphalts in the Silurian system of the Tarim Basin. One is the poor heavy oil layer with lower oil saturation in trap and the other is scattered hydrocarbon distributed along the transport layer and unconformity surface. Reservoir bed\|differentiated asphalts have two characteristics: total hydrocarbon content is high in extractable organic matter and the ratio of saturated to aromatic hydrocarbon is usually greater than unity. The physically modeling experiment has confirmed these characteristics and the genesis of the reservoir bed\|differentiated asphalts.

Mutual impact of true triaxial stress, borehole orientation and bedding inclination on laboratory hydraulic fracturing of Lushan shale

Unconventional resources like shale gas has been the focus of intense research and development for two decades. Apart from intrinsic geologic factors that control the gas shale productivity (e.g. organic matter content, bedding planes, natural fractures, porosity and stress regime among others), external factors like wellbore orientation and stimulation design play a role. In this study, we present a series of true triaxial hydraulic fracturing experiments conducted on Lushan shale to investigate the interplay of internal factors (bedding, natural fractures and in situ stress) and external factors (wellbore orientation) on the growth process of fracture networks in cubic specimens of 200 mm in length. We observe relatively low breakdown pressure and fracture propagation pressure as the wellbore orientation and/or the maximum in situ stress is subparallel to the shale bedding plane. The wellbore orientation has a more prominent effect on the breakdown pressure, but its effect is tapered with increasing angle of bedding inclination. The shale breakdown is followed by an abrupt response in sample displacement, which reflects the stimulated fracture volume. Based on fluid tracer analysis, the morphology of hydraulic fractures (HF) is divided into four categories. Among the categories, activation of bedding planes (bedding failure, BF) and natural fractures (NF) significantly increase bifurcation and fractured areas. Under the same stress regime, a horizontal wellbore is more favorable to enhance the complexity of hydraulic fracture networks. This is attributed to the relatively large surface area in contact with the bedding plane for the horizontal borehole compared to the case with a vertical wellbore. These findings provide important references for hydraulic fracturing design in shale reservoirs.

层理面遇天然裂隙的页岩储层水力裂缝网络复杂性研究

水力压裂形成复杂裂缝网络是页岩气高效开发的前提条件,其中层理面和天然裂隙的空间展布直接影响着水力裂缝扩展过程及其裂缝网络形成的复杂性。论文结合软件COMSOL Multiphysics和MATLAB,考虑页岩储层非均质性建立渗流-应力-损伤耦合模型,引入基于盒数法的网格覆盖法测定其复杂裂缝网络的分形维数,评价数值模拟的压裂效果,揭示层理面与天然裂隙共同作用的水力裂缝网络复杂性。研究结果表明:(1)层理抗拉强度和角度对水力裂缝网络复杂程度的影响显著,表现为抗拉强度较低或较高时,都不易形成复杂的水力裂缝网络;而较大角度层理的页岩储层更易形成复杂的水力裂缝网络。(2)天然裂隙抗拉强度较低时,容易被激活并诱发水力裂缝的扩展路径改变,增大裂缝网络的分形维数及复杂性。特别是天然裂隙与最大主应力方向的夹角较大时,显著改变水力裂缝的扩展路径,形成分形维数较高的更复杂的裂缝网络。(3)大小适中的应力比更易形成复杂的裂缝网络,论文提出的应力比1.5时,形成的裂缝网络分形维数最大,其复杂程度最高。其研究成果可为页岩储层水力压裂效果评价及压裂技术优化提供科学依据。

四川凉山州地质灾害灾情特征与主要致灾类型

凉山州受活动构造、地形地貌、河流切割等作用,是四川省地质灾害高风险地区。为系统查明凉山州地质灾害发育特征、灾情特征及主要致灾类型,采用资料收集、数理统计、现场调查等方法,统计分析地质灾害数据、灾情数据和重大突发地质灾害实例。结果表明:凉山州地质灾害以滑坡、泥石流为主,滑坡主要为中小规模土质滑坡,泥石流主要为中小规模沟道型泥石流;有记录以来共计发生24起死亡10人以上的地质灾害;2006—2020年,共发生46起地质灾害灾情,以泥石流为主。总结提炼了7种地质灾害主要致灾类型,红层滑坡是凉山州滑坡主要类型之一,遇水易软化解体,自稳能力差;复活型古滑坡,在凉山州多有分布,由于人类工程活动、河流冲刷等因素,古滑坡易变形和复活;库岸型滑坡,主要发育在木里县、布拖县、宁南县的水电站库区内,受库水位消落带影响斜坡塌岸隐患较多,坡体稳定性降低形成滑坡;含煤层型滑坡,主要发育在凉山州南部的煤系地层区域,斜坡前缘不合理开挖易诱发前缘滑塌并造成整体滑动;矿渣型泥石流是凉山州泥石流主要类型之一,矿渣、废石、尾砂等不合理堆放,为泥石流提供了丰富物源;凉山州常发生森林火灾,火烧迹地遭遇暴雨后易诱发火后泥石流;在构造活动强烈、山势陡峭的沟谷上游发生崩滑灾害后,易沿沟运动冲出,堵塞河道形成链式灾害。研究成果可为凉山州针对性开展防灾减灾工作提供数据支撑和科学参考。

海孜煤矿深部勘查区中组煤层气储层物性特征分析

【目的】煤层气储层的物性特征是进行煤层气开发研究的关键因子。【方法】重点对海孜煤矿深部勘探区域中组煤储层的物性参数进行调查,以对井田内中组煤储层物性特征进行研究。【结果】研究表明,煤层的物性特征适宜开采,其中有机显微组分占优,无机显微组分次之。该煤层含气量多,虽然煤层渗透率相对较小,但符合煤层气开采条件。煤层开采时的吸附作用一般,但有利于煤层气储集和缩短煤层气的开发周期。【结论】研究结果可为该研究区煤层气抽采提供可靠的技术参考。

吉木萨尔凹陷二叠系芦草沟组页岩油储层天然裂缝特征与压裂模拟

综合利用岩心、地震、测井和微地震监测等资料,在天然裂缝模型和地应力模型的约束下,运用页岩储层压裂缝网模拟研究了吉木萨尔凹陷二叠系芦草沟组天然裂缝特征及其对压裂缝网扩展的影响。研究结果表明:(1)吉木萨尔凹陷二叠系芦草沟组天然裂缝包括层理缝和构造缝,以层理缝为主,数量多、倾角小,裂缝数量平均为251条,裂缝面密度为0.58~1.34条/m,平均为0.93条/m。构造缝倾角为70°~95°,裂缝数量明显少于层理缝,根据形成时间及产状,构造缝可分为Ⅰ类和Ⅱ类构造缝。(2)研究区最小水平主应力为50.41~55.22 MPa,最大水平主应力为53.52~74.43 MPa,有利于水力压裂缝网的延伸,芦草沟组纵向存在应力隔层,最大层间应力差可达12 MPa,水力压裂时人工裂缝不易穿层。(3)研究区芦草沟组页岩压裂改造以激活高角度构造缝为主,96.45%的压裂缝为“T形”裂缝,而“十字形”和“一字形”压裂缝仅占2.24%和1.21%,芦草沟组压裂缝半缝长度为70~100 m,高度为10~30 m,邻近断层时由于缝长过大,易发生井窜。

鄂尔多斯盆地中东部奥陶系盐下层系白云岩储层沉积特征及发育演化机理

鄂尔多斯盆地马家沟组盐下的碳酸盐岩—蒸发岩层系是未来油气勘探的重要接替层系。由于碳酸盐岩—蒸发岩的特殊沉积组合强烈影响后续差异化成岩流体溶蚀—充填作用,进一步增大了盐下碳酸盐岩储层的复杂性,也给优质储层的分布预测增加了难度。本文以鄂尔多斯盆地马家沟组中下组合为研究对象,基于岩心、薄片、物性资料等开展储层地质学研究,识别出15种岩石类型和10类相序组合,明确了盐下储层类型包括:膏模孔泥晶云岩储层、颗粒白云岩储层、斑状白云岩储层、晶粒白云岩储层和微生物白云岩储层。在孔隙成因和演化分析基础上,建立了“优势沉积相+早期成孔+膏盐岩封盖保存孔隙”的盐下白云岩储层发育地质模式。研究结果深化了对盐下碳酸盐岩层系孔隙形成和保存机理的认识,同时对鄂尔多斯盆地的油气资源勘探开发具有重要的现实意义。

金沙江下游三堆子河段卵石推移质输沙率公式研究

金沙江上中游梯级水库运用后,进入下游的悬移质输沙量大幅减少,水沙条件显著变化;同时,卵石推移质输沙量在总输沙量中的比重明显增加,对水库淤积进程影响显著,开展变化水沙条件下金沙江下游卵石推移质输移规律研究具有重要意义。基于下游入口三堆子水文站2008—2021年卵石推移质实测资料,对经典起动流速公式和推移质输沙率公式进行了检验与修正。结果表明:与经典起动流速公式计算结果相比,通过引入以卵石粒径为变量的系数,所得到的不同粒径范围的卵石推移质起动流速修正公式,计算精度显著提高;经典推移质输沙公式的计算结果在输沙强度较低时与实测值偏差很大,通过建立输沙强度与水流强度的关系,并引入隐暴参数对公式进行修正,明显提升了其在低输沙率情况下的计算精度。修正后的起动流速公式和推移质输沙率公式能更有效地反映三堆子河段卵石推移质的输移规律。

吉木萨尔凹陷芦草沟组层理页岩渗吸置换规律

为研究吉木萨尔凹陷二叠系芦草沟组层理页岩储集层压裂后渗吸期间原油的动用规律,采用岩心渗吸置换实验结合核磁共振技术,定量描述不同孔隙内原油的相对含量。采用吉木萨尔地区上甜点的岩心开展渗吸实验,研究重力作用、各向异性、重力分异和水力压裂裂缝宽度对渗吸置换影响,并进行定量表征。结果表明:层理页岩自发渗吸的过程中,重力作用在渗吸中起到了动力作用,顶部渗吸的采收率高于水平渗吸;各向异性对层理页岩渗吸的影响较大,压裂液进入平行于层理的渗吸置换量大,达到渗吸平衡的时间较垂直于层理短,平行于层理渗吸采收率高于垂直于层理;重力分异是指在岩心底部渗吸时,渗吸置换出原油而停留在岩层表面形成油膜,阻止压裂液继续进入基质,导致渗吸效果变差,底部渗吸采收率与顶部渗吸采收率相差14.12%;模拟水力压裂裂缝宽度为2 mm的条件下发生渗吸置换的液量有限,导致模拟裂缝内含水饱和度下降快,限制了渗吸的进一步进行。因此,裂缝的缝高方向应尽量穿过平行层理,增大裂缝宽度,增加裂缝改造体积。

PLA/EC共混制备自降解暂堵剂及性能评价

以聚乳酸为主剂,将其与乙基纤维素、腰果酚NSF3、纳米碳酸钙进行熔融共混改性,制备了新型自降解暂堵剂。通过扫描电镜分析和热重分析测试,对暂堵剂的结构进行表征,考察了自降解暂堵剂体系的降解性能、配伍性能、砂床封堵性能、储层保护性能等指标。结果表明,当聚乳酸和乙基纤维素的比例为4∶6时,暂堵剂具有较好的降解性能和热稳定性。90℃、pH=9的条件下,5d的降解率小于30%,15d的降解率大于90%,满足水平钻井作业要求。温度达到223℃时,质量损失仅为0.35%。在钻井液中加入质量分数为3%的暂堵剂后,在0.69MPa压力下,30min侵入石英砂床的深度小于5cm,能起到良好的封堵作用。此外,该暂堵剂与钻井液的配伍性良好,具有降滤失作用,且解堵后不同岩心的渗透率恢复值均在85%以上,具有较好的储层保护性能。

水力压裂多裂缝扩展诱发光纤应变演化试验研究

为解决光纤监测水力压裂过程中裂缝扩展形态认识不清的难题,提出了一种基于光纤应变监测的水力压裂物理模拟试验方法。将基于光频域反射(OFDR)技术的分布式光纤解调器与大型真三轴压裂物理模拟试验相结合,开展了人造试样及页岩试样水力压裂光纤实时监测物理模拟试验。试验结果表明,基于OFDR的分布式光纤传感技术可以高空间分辨率、高精度监测应变的演化,光纤的应变数据可以清晰地反映裂缝的产生、扩展和闭合。根据试验结果提出了一种基于光纤应变感测的水力压裂裂缝形态判别准则,该准则可以根据光纤应变演化信息判断部分裂缝类别。研究结论可高效地指导分布式光纤数据解释工作,可为光纤压裂监测的现场规模应用提供参考。

层理倾角与孔道直径对页岩单轴破坏特征影响的数值研究

为探究深部地下工程中层状围岩井壁与隧道失稳破坏机理,通过构建单轴压缩条件下随机分布层理面的空心页岩数值模型,研究了层理倾角与孔道直径对含孔道页岩强度及破坏特征的影响。数值模拟结果表明:(1)含孔道页岩强度随孔径的增大逐渐减小,随层理倾角变化表现出各向异性特征且各向异性指数随孔径增加而增大,层理面与轴向力夹角影响层理面作用机理造成失稳模式的各向异性,孔道存在使受力面含缺陷造成加载中应力集中不均匀、传递路径不连续从而使页岩试样失稳强度降低;(2)在层理面与孔道共同作用下,页岩表现出各向异性的脆性破坏形式:层理0°时为沿层理与基质面的滑剪破坏,层理30°、60°时表现为沿层理面的滑移破坏,层理90°时为贯穿试样的劈裂破坏。层理倾角较小时完整页岩和含孔道页岩在破坏形式上无显著区别,层理倾角较大时含孔道页岩两侧裂纹出现差异且主裂纹随孔径增大而上移。(3)破坏时输出的声发射信号受孔径影响并随孔径增大出现不同程度的降低,通过声发射信号变化规律与时空分布特征能够评估破坏烈度并再现试样内部细观结构渐进损伤特征。研究结果有助于理解含孔道页岩失稳破坏机理,可为提升地下工程的稳定性和安全性提供理论指导。

三门峡水库原型试验以来渭河下游河床稳定性变化及其影响因素

为探究渭河下游河道形态演变特征及影响机理,基于多年水文观测资料分析渭河下游河床稳定性演变规律,探讨三门峡水库原型试验以来(2003~2020年),来水来沙条件、潼关高程变化、河道边界条件与河床稳定性的响应关系。结果表明,原型试验期内,渭河下游河道年均径流量呈缓慢增加趋势,年均含沙量均呈缓慢减小趋势,河段河槽呈扩张趋势,潼关高程呈逐年下降趋势。原型试验期前后,渭河下游河段河床横向、纵向和综合稳定性系数均增加,原型试验期内,河床稳定性呈逐年上升趋势。前期3年平均水流冲刷强度和潼关高程变化是影响渭河下游河床综合稳定性的重要因素,利用多元回归分析方法建立了渭河下游河床综合稳定性的经验计算公式,验证了所提经验公式的准确性和可靠性。研究成果可为渭河下游及类似河流管理提供参考。

渝东南南川地区深层煤层特征与煤层气赋存状态研究

基于煤田钻孔资料、煤岩岩心及镜下观察,开展了重庆南川地区煤系储层岩心数字化、液氮吸附、CO_(2)吸附、高压压汞、气相色谱、等温吸附等一系列分析检测测试,分析并讨论了深层煤储层特征、煤层气赋存状态及影响因素。研究表明:①南川区块深部煤层发育,奠定煤层气形成的良好基础。②微裂缝是煤储层的主要储集空间,控制了气体的渗流作用。微孔隙的存在是气体吸附的主要原因,喉道控制了煤层气的微观渗流。③煤的吸附能力随变质程度增加而增大,与压力正相关,与温度负相关。浅层及中深层(1500 m以浅)煤层气吸附量对压力较为敏感,深层(1500 m以深)煤层气吸附量对温度更为敏感。④深层煤层具有“中高演化、微裂隙发育、高含气、富含游离气”的特征,游离气为煤岩解吸提供了大量气源。

考虑劣化效应的顺层灰岩岸坡滑移-拉裂研究

三峡库区在高程145~175 m之间的周期性水位调控,促使库区巫峡段灰岩岸坡劣化损伤加剧,稳定性衰减。通过引入劣化深度L 0以及岩层滑移厚度H建立了滑移-拉裂计算模型,研究巫峡段顺层灰岩岸坡受侵蚀劣化脱空时的滑移-拉裂破坏。研究结果表明:当L 0不变时,随着H增加,岸坡易于失稳且失稳距离x明显增大;随着L 0变大,同一H岩层面滑移失稳距离x明显变大,可增加约3倍有余,岩层面参数的劣化衰减使顺层岸坡更易发生深厚层、大规模的失稳破坏;当L 0较小时,易沿坡肩后部“滑移-拉裂”破坏,随着L 0逐渐变大,破坏模式变为坡肩前后部同时发生滑移-拉裂失稳。针对岩层面易受库水损伤的顺层岸坡,治理方案建议为:坡肩及后缘滑移块锚索(杆)加固+坡肩前缘岩层出露面“挂网+喷浆+随机锚杆”组合方案,以达到“固头”以及隔绝“劣化损伤”通道的目的。研究成果可为库区内顺层灰岩岸坡岩体劣化稳定性分析以及工程治理提供一定技术参考。