Fluvial facies is controlled by high-frequency base-level changes and frequent migration, evolution, erosion, and superimposition, forming structurally complex and strongly heterogeneous reservoirs. This leads to poor efficiency of oil recovery and dispersed remaining oil in fluvial facies oil fields, resulting in a much lower recovery rate compared to marine sandstone reservoirs. Based on the theory of Fluvial reservoir configuration, this paper proposes a set of quality characteristic parameters for complex sand bodies, which describe the characteristics of the reservoir architecture including the parameters related to structural features, geometric features, physical properties, and heterogeneity characteristics. The paper also proposes that the scale of the reservoir is a necessary condition for forming high-quality reservoirs, and the reservoir structure is the key factor controlling reservoir quality. Using the guidance of the complex sand body quality characteristic parameter and the reservoir quality control mechanism, an improved distance clustering method based on principal component analysis is used to establish a quality evaluation process for complex sand bodies.Taking the R23 unit of the lower section of the Minghuazhen Formation in the Qinhuangdao 32–6 oil field as an example, the optimal quality of complex sand bodies is evaluated. The best type of complex sand body has a larger sand body thickness, which is a superimposed or closely stacked complex point-bar sand body. The complex sand body has a simple sand body structure, good connectivity, and high initial and cumulative production, with good development effect. However, the bottom of the sand body is generally quickly flooded with water, and remaining oil is mainly distributed in the upper part of the sand body. The quality of the second and third types of complex sand bodies is moderate, and the exploitation effect is poorer than that of the first type of reservoir. They can be used as targets for adjusting the potential of production in the later stage of oil field development.

In recent years, with the continuous discovery of Mesozoic buried hill oil and gas reservoirs in the Bohai Sea area, oil and gas discoveries have been found, but there are significant differences in production capacity. However, research on the influencing factors of volcanic rock oil and gas production capacity differences in the study area has not yet been carried out. The K oilfield in Laizhou Bay Depression is one of the buried hill oil and gas reservoirs. In order to further clarify the reservoir characteristics of the oil reservoir and provide a basis for the formulation of oilfield development plans, a systematic study was conducted on the volcanic rock facies types, physical properties, reservoir space, and main control factors of the oil reservoir using data such as rock cores, sidewall cores, and scanning electron microscopy. The results show that the Mesozoic reservoir in this area mainly develops 11 kinds of rocks, including volcanic clastic rock, pyroclastic lava, lava and sedimentary volcanic clastic rock, as well as three kinds of lithofacies, including explosive facies, volcanic sedimentary facies and effusive facies. The fourth well area is dominated by explosive facies heat wave and pyroclastic flow, and effusive facies simple lava flow; Its storage space includes pores and fractures, with pores including intergranular dissolution pores, devitrification pores, clay intergranular pores, and mold dissolution pores. The four well areas are mainly composed of intergranular dissolution pores; Cracks mainly include structural cracks and weathering cracks; The Mesozoic reservoirs in this area are mainly controlled by three factors: lithology, lithofacies, dissolution, and geological models. Based on comprehensive analysis, it is believed that the thermal wave near source facies and thermal debris flow near source facies are relatively advantageous reservoirs in the study area, laying the foundation for predicting favorable reservoirs.

In recent years, the oil and gas reserves discovered in shallow water deltas in China have continued to grow. The research on shallow water delta deposition models and depositional genesis is becoming more and more mature. In this latest discovery, a unique type of extremely narrow channel shallow water delta deposit was found at the top of the V oil group in the lower part of the Minghuazhen Formation during the Neogene period at DL-A Oilfield, located in the Bohai Bay Basin. The width of most single channels in this deposit measures between 100 and 200m, which is relatively rare and differs from existing research. To better understand this unique narrow channel shallow water delta deposit, a range of analysis methods were conducted including trace element analysis, major element analysis, grain size analysis, core observation, casting thin section observation, 3D seismic analysis, and other methods. These analyses were used to determine the sedimentary environment and sedimentary genesis of the deposit in the study area. The results show the following: (1) The top of the V oil group in the lower part of Minghuazhen Formation was deposited with a strong oxidizing environment. In the early stage, the climate was dry and cold, and gradually changed to warm and humid in the late stage. (2) Due to the frequent exposure to the surface, obvious weathered surfaces and sedimentary discontinuities were observed on the cores; the particle size analysis shows that the lamina types developed in the study area are clastic–clay laminae and clay–clastic laminae, which are mostly developed in shallow lakes area. (3) Observations of cores and thin sections also indicated that the hydrodynamic conditions frequently changed in the study area, alternating between strong and weak hydrodynamic conditions in a short period due to the alternating occurrence of flood and dry periods during the rainy season. Weak hydrodynamic conditions and slow water flow result in insufficient undercutting and sidecutting of rivers. The alternating occurrence of flood periods and dry periods has led to the development of crevasse splays and frequent river channel diversions, resulting in the inability of long-term stable development of the river channel. Besides, the change of water level has also led to the rebuilding of the river. Therefore, the multiple effects led to the formation of an extremely narrow channel shallow water delta. The accuracy of the sedimentary model is verified by a comparative study of the Shaliu River and Buha River in the modern Qinghai Lake. The new extremely narrow channels deposition model proposed this time further improves the deposition theory. At the same time, the modern depositional characteristics of the Shaliu River and Buha River also reveal the reservoir deposition between channels that cannot be distinguished by seismic data, providing guidance for the development of oil and gas in the study area.

H Oilfield in the Pearl River Mouth Basin mainly develops delta front deposits. Its reservoir thickness is thin, the lateral change is fast, and the understanding of lithologic boundary and sand body connectivity is not clear, which seriously restricts the efficient development of oil field. Seismic waveform indication inversion can fully use the lateral changes of seismic waveforms to carry out high-frequency component estimation, and establish the interpolation model which is more consistent with the sedimentary characteristics. This method has good inter-well prediction ability, and is particularly suitable for high-precision prediction of fast lateral changes, strong non-average, and thin interbedded sand and mudstone reservoirs. While for another method, seismic sedimentology, is to use the seismic attribute slice to describe the lateral distribution range and sedimentary characteristics of the reservoir under the guidance of isochronous stratigraphic framework. It has a good detection effect on the plane sedimentary characteristics of thin reservoir which cannot be resolved vertically. Combined with the above two methods, a set of technical processes for fine description and sedimentary characterization of marine thin sandstone reservoirs is formed and has achieved good application results in H Oilfield, meanwhile provides effective technical support for remaining oil prediction and potential tapping adjustment in the study area.

在油田开发中后期,砂层组或小层级别的砂岩储层内部构型剖析与表征逐渐成为储层研究的重点.在少井条件下充分挖掘地震资料信息,建立储层内部结构特征的地震响应关系,发展"以地震信息为导向,井震联合"的方法,成为海上油田储层构型研究的有效途径.通过井点处曲线形态、砂体厚度、垂向高程差异等信息对砂体期次的刻画,以及结构类敏感地震属性对砂体边界的预测,开展复合砂体的垂向分期与侧向划界,能够实现储层构型的剖析.结合海上油田的资料基础和开发特点,形成一套储层构型的结构和成因表征方法:分析沉积类型及其对砂体展布的控制机理,构建沉积模式;优选敏感地震属性,预测储层内部结构;标定井震资料的地质含义并转化为合理参数;综合多信息编制地质图件.

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.