On the basis of “Carbon Peak and Carbon Neutral” goals, carbon sequestration projects are increasing in China. The integrity of cement sheaths, as an important factor affecting carbon sequestration projects, has also received more attention and research. When CO2 is injected into the subsurface from sequestration wells, the cement sheath may mechanically fail due to the pressure accumulated inside the casing, which leads to the sealing of the cement sheath failing. The elasticity and strength parameters of the cement sheath are considered in this paper. The critical bottom-hole injection pressures of inclined well sections under anisotropic formation stresses at different depths were calculated for actual carbon-sealing wells in the X block—the CO2 sequestration target block. The sensitivity factors of the critical bottom-hole injection pressure were also analyzed. It was found that the cement sheath damage criterion was tensile damage. The Young’s modulus and tensile strength of the cement sheath are the main factors affecting the mechanical failure of the cement sheath, with Poisson’s ratio having the second highest influence. An increase in the Young’s modulus, Poisson’s ratio, and tensile strength of the cement sheath can help to improve the mechanical stability of cement sheaths in CO2 sequestration wells. This model can be used for the design and evaluation of cement in carbon sequestration wells.

The target formation in the study area of the Pearl River Mouth Basin is characterized by complex lithology and thin interbedded layers, with a large pore-permeability distribution range and strongly heterogeneous characteristics, which makes the reservoir pore structure and production capacity significantly different and brings research difficulties for reservoir logging evaluation and desert identification. The conventional reservoir classification method is mainly based on physical research, which requires developing extremely accurate formulas for calculating porosity and permeability; the calculation accuracy of pore permeability of low-porosity and low-permeability reservoirs is difficult to guarantee; and the conventional logging data cannot be comprehensively applied in reservoir classification. In this paper, taking Zhujiang and Zhuhai Formation reservoirs in the Huizhou M oilfield as an example, we integrated core analysis data such as core cast thin section, pore permeability data, rock electrical parameters, grain size, and relative permeability curves and combined with petrophysical parameters and pore structure characteristics to classify the reservoirs. The artificial neural network is used to predict the resistivity of saturated pure water (R0) to remove the influence of oil and gas on reservoir resistivity. The natural gamma ray (GR) “fluctuation” is used to calculate the variance root of variation (GS) to reflect the lithological variability and sedimentary heterogeneity of the reservoir, and then the conventional logging preferences, R0 and Gs (based on GR), are classified based on the automatic clustering MRGC algorithm to classify the logging facies. To classify the petrophysical phase reservoirs under the constraint of pore structure classification, we proposed a petrophysical classification logging model based on the natural gamma curve “fluctuation” intensity for strongly heterogeneous reservoirs. The learning model is extended to the whole area for training and prediction of desert identification, and the prediction results of the model are in good agreement with the actual results, which is important for determining favorable reservoirs in the area and the adjustment of oilfield development measures.

渤海油田储层类型以河流相复合砂体为主,在长期注水开发后已经进入高含水、特高含水阶段,砂体复合程度如何影响剩余油的形成与分布目前尚不明确.因此,研究剩余油的形成与分布情况,提出最优井网匹配模式,是目前油气田开发工作者关心的重点.利用数值模拟手段,建立具有不同复合程度的典型地质模型,开展了非均质储层井网匹配模式与井间剩余油分布研究.结果表明:当平面非均质模型各层间无隔层时,采取直井井网开发后,全区水驱后全区剩余油饱和度降低幅度最大,降低22.69％,其次为直井注水平井采联合井网,再次为水平井井网.当垂向非均质模型各层间无隔层时,采取水平井井网开发后,全区水驱后全区剩余油饱和度降低幅度最大,降低22.86％,其次为直井注水平井采联合井网;当层间有隔层时,采取直井注水平井采联合井网开发后,全区水驱后全区剩余油饱和度降低幅度最大,降低20.96％.

渤海油田在长期注水开发后进入高含水、特高含水阶段,大量剩余油以不同规模、不同形式分布于储层中.其储层类型以河流相复合砂体为主,为了了解复合砂体构型如何影响注入药剂波及效果、剩余油形成与分布等,开展了砂体构型对"调剖+调驱+驱油"效果影响实验研究.结果表明:聚合物溶液与Cr3+交联剂发生反应形成聚合物凝胶,作为调剖剂可对储层产生良好的封堵效果,聚合物微球调驱剂具有较强的吸水膨胀能力,初期粒径为8.7μm,缓膨3 d后粒径增加至27.7μm,表面活性剂驱油剂具有较好的界面张力效果,当质量浓度达到2000 mg·L-1时,油水界面张力可降至10-2数量级.当岩心模型为主体切叠型垂向复合砂体构型特征时,渗流阻力较低,水驱采收率和各阶段采收率均高于侧缘接触型复合砂体构型特征.

The reservoir heterogeneity of Q oilfield is more severe after long-term water injection development, and water flooding is ineffective. In this study, the combined technologies of profile control, profile control and flooding, and oil displacement were proposed to improve the water flooding development effect. Then, the influence of the well pattern type on the remaining oil distribution, after development, was investigated. Cr3+ polymer gel, which has an optimal gel-forming effect, was used as the profile control agent. Moreover, the entire molecular structure had a “network” structure. A polymer microsphere was used as a profile control and flooding agent, which showed a good hydration expansion capacity. The initial particle size distribution had a range of 7.2–11.1 μm, and the expansion multiple was 4.35–5.64 after 7 days. The surfactant was an oil displacement agent, and the interfacial tension was approximately 5.08–5.11 × 10−1 mN/m. After the “profile control + profile control and flooding + oil displacement” technologies, the horizontal well pattern had a large seepage area. The effect of expanding the sweep volume was significant, and the remaining oil saturation in each stage was lower than those of the vertical and horizontal–vertical combined well patterns. Compared with the first water flooding stage, the remaining oil saturation values of the three permeable layers changed by 11.9%, 17.3%, and 19.8% during the subsequent water flooding stage.

复合点坝是由多期残缺点坝组合在一起形成的复合体,储层内部结构复杂、非均质性强.以往关于点坝的研究,多是从点坝的形态、粒度、规模和水动力成因去分析,极少从点坝形成的"残缺性"做定量研究和成因分析.选取阿尔伯塔盆地下白垩统McMurray组的地震切片、密西西比河New Madrid曲流河段卫星照片、曲流河数值模拟和物理模拟等资料,统计拟合复合点坝演化阶段和复合度的关系,在二维坐标轴投点后,都可以拟合得到一条相似的对数曲线y=-alnx+1.得出复合点坝演化符合以下规律:某一期点坝从形成至被破坏成残缺状态,其残缺程度(复合度)与演化阶段呈对数递减关系.该结论对曲流河理论研究和砂体表征都具有一定价值.

复合点坝储集层内部非均质性分析是曲流河研究的难点,仅靠地震和测井资料难以解释清楚.关于复合点坝储层构型表征也较缺乏定量化指导标准.本研究选取了13条曲流河河段的260个复合点坝作为数据样本,进行参数分类统计,形成曲流河复合点坝地质知识库.将复合点坝分为4大类、25个亚类;将侧积体分为8大类、22个亚类.统计不同类型复合点坝和侧积体构型样式的分布概率关系.以此为基础,充分利用定量分布概率关系,达到在资料较少情况下分析复合点坝储集层平面非均质性的目的.

复合点坝侧积体定量成因分析是河流沉积学研究的难点之一.通过选取密西西比河下游段激光雷达数据,剖析复合点坝侧积体的内部特征,统计侧积体高程数据,发现其符合周期变化的特点.对高程数据进行傅里叶变换计算,得到复合点坝侧积周期,将侧积周期与河道规模进行拟合,两者符合线性关系,拟合度高.深入分析后,认为侧积周期受河流的季节性洪泛周期控制.研究结论为侧积体定量成因分析提供了理论依据.

通过浅水三角洲现代沉积考察分析,结合探地雷达(GPR)资料,对浅水三角洲分类方案和对应的沉积模式进行探讨.结果 表明:根据分流河道弯曲指数和分叉参数,将浅水三角洲分为分叉平直河三角洲、分叉曲流河三角洲、分汇曲流河三角洲和分汇辫状河三角洲4种类型,并建立了各类型的沉积模式;浅水三角洲沉积模式的控制因素是分流河道下蚀作用和侧蚀作用的强度.将该沉积模式应用于渤海南部海域BZ25-1油田新近系明化镇组下段砂体内部构型的研究认为:明化镇组下段4油层组2小层(NmⅣ2)时期是低位体系域早期,发育分汇曲流河三角洲,河道间为侧积隔夹层;明化镇组下段4油层组1小层(NmⅣ1)时期湖平面上升,发育分汇辫状河三角洲,河道间为垂积隔夹层.这为下一步的开发方案设计提供了指导.

滩坝砂体研究是辽河西部凹陷曙北地区断陷湖盆勘探的新领域.文章分析了曙北滩坝砂体的主要控制因素是古地貌、古水深、古物源和古风场等,即"风—源—盆"三端元系统,并提出了定量恢复四个控制因素的方法.结果表明,曙北滩坝主要发育于微观古地貌水下低隆起部位;形成曙北滩坝有利水深大约7m;滩坝物源来自于三角洲改造、古潜山剥蚀和岸线基岩侵蚀;滩坝的形成受到南北季风影响,风力达8级.根据控制因素将曙北滩坝发育区分为沿岸带、潜山带、潜山披覆带、北部斜坡带和深洼带五个带,其中潜山披覆带最有利于滩坝发育.

Gravelly beach ridges, which are formed solely by swash processes, may accurately reflect past wave conditions. The thickness (or height) of a gravelly beach ridge approximately equals the height of wave inundation, which is the sum of the surge and wave run‐up. Their ancient counterparts, if well‐preserved and identified, can be used to estimate palaeowave conditions, which can later be converted to palaeowind intensities based on wind–wave relationships. A technique is described for estimating the palaeowind speed in this paper, which is referred to as the gravelly beach‐ridge thickness technique. By comparing these estimates with instrumental wind records obtained at a modern lake, Qinghai Lake in north‐western China, the beach‐ridge thickness technique is shown to be useful for estimating the average wind speed (Vavg). When applying this method to ancient fetch‐limited basins, five parameters are necessary: (i) the thickness of the isolated gravelly beach ridge; (ii) the average depth of the water body; (iii) the palaeofetch; (iv) the angle between the palaeowind direction and the normal to the shoreline; and (v) the particle size. This technique was applied to an ancient example in the Eocene Dongying Depression, located in eastern China. The results indicate that the average wind speed of the northern wind ranged between 2·27 m sec−1 and 8·36 m sec−1 from 45·0 Ma to 42·0 Ma, and displayed a generally decreasing trend that included early strengthening followed by weakening and later strengthening during this period. The beach‐ridge thickness technique provides a new perspective on delineating palaeowind conditions and can be applied to ancient fetch‐limited basins with gravelly beach ridges worldwide. Generally, if a water body is sufficiently large (fetch exceeding 40 km), deep (average depth exceeding 10 m) and waves (or winds) are determined to approach the shoreline with high angles (angle of incidence <35°), then the calculation errors will be small to negligible.

It has been known that both extensional and transtensional tectonics commonly trigger a one-cycle evolution of lake sediments, but lake-cycle development co-controlled by extensional and transtensional tectonics still need identification. Here we report a double-cycle of lake sediments formed in extensional to transtensional phases in the Paleogene Nanpu Sag of the Bohai Bay Basin, China. The sag successively experienced five phases of lake-type evolution, characterized by: 1) overfilled, 2) balanced-fill, 3) overfilled, 4) balanced-fill, and 5) overfilled. Extensional tectonics was responsible for the opening of the basin and the initial creation of accommodation (1st through 3rd phase). Next, subsidence increased again through transtensional tectonics resulting in the creation of new accommodation (4th–5th phases). Investigations show this double-cycle lake-type evolution is also present in other lake-basins with similar tectonic settings (e.g., both extensional and transtensional tectonics). A different exploration and exploitation strategy should be devoted to the double-cycle evolution of lake basins controlled by extensional to transtensional tectonics in comparison to the single-cycle evolution in extensional or transtensional lake basins.

Based on the sedimentary and tectonic background of the Termit Basin, this paper focuses on the Upper Cretaceous Yogou Formation and uses organic geochemistry, logging, oil testing and seismic data to analyze the primary control factors of the hydrocarbon accumulation and establish corresponding model in order to predict favorable exploration target zones of hydrocarbon reservoirs. This study demonstrates that the Upper Cretaceous Yogou Formation is a self-generation and self-accumulation type reservoir. The Yogou Formation hydrocarbon reservoirs in the Koulele area are controlled by four factors: (1) the source rock is controlled by a wide range of YS1-YS2 marine shale, (2) the sandstone reservoir is controlled by the YS3 underwater distributary channel and storm dunes, (3) migration of hydrocarbons is controlled by faults and the regional monocline structure, and (4) the accumulation of hydrocarbons is controlled by lateral seal. The structures in the western Koulele area are primarily reverse fault-blocks with large throws, and the structures in the east are dominantly fault-blocks with small throws (co-rotating and reverse) and a fault-nose. In the western Koulele area, where the facies are dominated by storm dunes on a larger scale, it is easier to form lithologic reservoirs of sandstone lens. In the eastern Koulele area, high-quality channel sandstone reservoirs, fault-blocks with small throws, and the monocline structure benefit for the formation of updip pinch out lithologic traps, fault lithologic reservoirs and fault-nose structural reservoirs. Future exploration targets should be focused in the western storm dunes zone and eastern distributary channel sand zone with small fault-blocks.

Taking the Es82 Formation in the second district of Shengtuo Oilfield as an example,using the cores,dynamic monitoring data and dense well condition,this paper adopts the research methods of hierarchical control and dynamic fit.It analyzes the types,causes and architecture hierarchy of barrier-interlayers in the mouth bar.It also deeply discusses the position,shape,extending scale and distribution patterns of barrier-interlayers in different orders.The research shows that barrier-interlayers can be divided into three types:muddy barrier-interlayers,calcareous interlayers and physical barrier-interlayers.Five-order barrier-interlayers limit the composite mouth bar.Five-order barrier-interlayers which contain muddy barrier-interlayers,calcareous interlayers and physical barrier-interlayers are located at the top of the composite mouth bar.Muddy barrier-interlayers and physical barrier-interlayers are lateral stitching,sheet size and easy to form a stable barrier.Calcareous interlayers are discrete and non-continuous.Four-order interlayers limit a single bar.Four-order interlayers are located at the stacking part of single bars.Muddy,physical and calcareous interlayers of four-order extends along the top of the single bar.They are oblique crossing laterally and discrete.There-order interlayers limit the proliferative bodies.Muddy,physical and calcareous interlayers of there-order are multiple,thin,discrete and non-continuous.These interlayers distribute between the proliferative bodies and incline to the lake.

The lithologic-stratigraphic traps in lacustrine basins are controlled by slope-breaks. Beixi Slope in Hailaer Basin has the characteristics of slope-breaks. It is important to study the features and genesis of slope-breaks, and the control mode of sedimentary facies and lithologic-stratigraphic traps to help identify favorable exploration area. By the genetic mechanism of Beixi slope-breaks, we can divide them into fault slope-break, flexural slope-break, sedimentary slope-break and erosive slope-break. According to the relationships between slope-break and subsag, we divide the slope-break into three cells-inner slope-break, middle slope-break and outer slope-break. The outer slope-break is characterized by erosion slope-break, controlling the stratigraphic overlap traps;the middle slope-break is mainly fault slope-break and flexural slope-break, controlling the block-lithologic combination traps; the inner slope-break is mainly sedimentary slope-break, controlling the lenticular lithologic traps.

通过对岩石薄片及铸体薄片的观察和分析,结合大量物性及压汞分析资料,对辽河西部凹陷西斜坡沙四段砂岩储层的岩石学特征、成岩作用及储层物性特点进行了研究.结果表明,研究区岩石类型以长石岩屑砂岩和岩屑砂岩为主,常见压实、胶结、交代、溶蚀、蚀变等成岩作用类型;常见孔隙类型有原生粒间孔、粒间溶孔、粒内溶孔等,其中粒间扩大孔隙最常见;孔隙结构主要为细-中孔细喉型,储层类型主要为中孔低-中渗型,储层物性较好.主要分析了成岩作用对储层发育的影响,压实和胶结作用对储层具有破坏性作用,溶蚀作用对改善储层物性具有建设性作用.溶蚀作用形成的粒间溶孔、粒内溶孔、粒间扩大孔及超大孔隙对储层的贡献最大,形成了中-粗孔、中-高渗型优质储层.900～1 900 m和2 300 ～2 900 m深度段为孔隙度和渗透率异常带,带内溶蚀作用发育,在其中寻找有利的储层应当成为下一步勘探的重点目标.

古地貌是控制滩坝沉积的重要因素,决定了滩坝发育的规模与特征.运用印模法与层序地层学相结合的方法,通过残余厚度求取、真厚度校正、压实恢复、潜山剥蚀区确定和古水深恢复5个步骤,恢复辽河西部凹陷曙北地区沙四段层序2低位体系域主要滩坝砂体沉积时期的古地貌,据此分析研究区古地貌对滩坝沉积的控制作用.研究区古地貌总体上呈西高东低,西部为斜坡带,东部为洼陷带,斜坡带中部为古隆起区.根据古地貌特征将曙北地区分为沿岸带、潜山带、北部斜坡带、南部斜坡带和洼陷带5个地貌单元,滩坝砂体主要分布在沿岸带与古隆起周围.古地貌控制了湖盆水体的范围与相对深度、水动力的强弱分带、滩坝沉积的地形坡度、物源的搬运通道与卸载场所等滩坝沉积的影响因素,进而控制滩坝砂体的发育.

In the control of palaeogeomorphology and fracture, multistage slope break zones are developed in Beixi Slope. After the analyses of the structural-paleogeomorphologic features, according to the relationships between slope break zones and subsags, we divide the slope break zones into three cells—inner slope break zones, middle slope break zones and outer slope break zones. Compared with the outer and middle slope break zones, the fault block traps are richly developed in the inner slope break zones, which is nearer to the oil generating depressions. And the conditions of reservoirs there are good. So they are excellent for hydrocarbon accumulation and preservation with good oil accumulating conditions.

To identify the factors and mechanisms affecting reservoir micro-heterogeneity in the same type of microfacies at different stages of cycle, the main controlling factors of the reservoir micro-heterogeneity of the mouth bar in Es2-9 Formation of the Shengtuo Oilfield were analyzed based on the sedimentary dynamic analysis of high resolution stratigraphic sequence and quantitative parameters of reservoir micro-heterogeneity. The base level cycles of different stages have a differential control on the reservoir micro-heterogeneity of the mouth bar. The changes of the base level in different orders lead to variation in accommodation space and sediment supply, and in turn changes in sedimentary environments of mouth bar at different stages, as a result, the reservoir micro-heterogeneity of the single mouth bar in short-term base level cycle is strong at bottom and weak at top, the reservoir micro-heterogeneity of compound mouth bar (formed by different stages of single mouth bar) in middle-term base level cycle gets weaker from bottom-up, and the reservoir micro-heterogeneity of compound mouth bar at different stages of long-term base level cycle has no obvious pattern.