The lithofacies of matrix-type shales are diverse. Interbedded siltstones and shales, a combination that is known for excellent reservoir properties, are primary targets in terrestrial shale. We investigated the generation of shale oil and the charging processes in the interbedded shale/siltstone succession of the upper fourth member of the Shahejie Formation (Dongying Depression, Bohai Bay Basin). The charging process is categorized into four stages: (A) initial stage, (B) charging stage, (C) maximum charging stage, and (D) late charging. During stage A, the production of shale oil is minimal, the mobility is limited, and the stage division curve remains consistent. During the B stage, there was a rapid increase in shale oil production, OSI, and filling rate, accompanied by significant changes in the slope of the curve. The production of shale oil, along with the OSI and filling rate of the C stage, achieved peak values, and the stage division curve exhibited stability. During stage D, there is a rapid decline in shale oil production, accompanied by a reduction in the filling amount. By using petroleum geochemistry, microscopy and micro-CT detection we analyze the evolution of the properties of the shale oil, mineral compositions, reservoir spaces and shale oil occurrence in these different stages. A combination of thermal evolution degree, shale oil properties and mineral composition controls the enrichment of shale oil. During the medium to high thermal evolution stages, the shale oil dominated by light to medium-weight oil components predominantly occurs in a free state within abundant dissolved pores, intergranular pores, inter-crystalline pores and microfractures; this is the most favorable stage for the enrichment of shale oil. On this basis we develop a model for shale oil enrichment in matrix-type shales that are interbedded with siltstone layers; this may be useful in the exploration of shale oil in similar lithofacies.

Coal is a solid combustible mineral, and coal-bearing strata have important hydrocarbon generation potential and contribute to more than 12% of the global hydrocarbon resources. However, the deposition and hydrocarbon evolution process of ancient coal-bearing strata is characterized by multiple geological times, leading to obvious distinctions in their hydrocarbon generation potential, geological processes, and production, which affect the evaluation and exploration of hydrocarbon resources derived from coaly source rocks worldwide. This study aimed to identify the differences on oil-generated parent macerals and the production of oil generated from different coaly source rocks and through different oil generation processes. Integrating with the analysis of previous tectonic burial history and hydrocarbon generation history, high-temperature and high-pressure thermal simulation experiments, organic geochemistry, and organic petrology were performed on the Carboniferous-Permian (C–P) coaly source rocks in the Huanghua Depression, Bohai Bay Basin. The oil-generated parent macerals of coal's Secondary Oil Generation Process (SOGP) were mainly hydrogen-rich collotelinite, collodetrinite, sporinite, and cutinite, while the oil-generated parent macerals of Tertiary Oil Generation Process (TOGP) were the remaining small amount of hydrogen-rich collotelinite, sporinite, and cutinite, as well as dispersed soluble organic matter and unexhausted residual hydrocarbons. Compared with coal, the oil-generated parent macerals of coaly shale SOGP were mostly sporinite and cutinite. And part of hydrogen-poor vitrinite, lacking hydrocarbon-rich macerals, and macerals of the TOGP, in addition to some remaining cutinite and a small amount of crude oil and bitumen from SOGP contributed to the oil yield. The results indicated that the changes in oil yield had a good junction between SOGP and TOGP, both coal and coaly shale had higher SOGP aborted oil yield than TOGP starting yield, and coaly shale TOGP peak oil yield was lower than SOGP peak oil yield. There were significant differences in saturated hydrocarbon and aromatic parameters in coal and coaly shale. Coal SOGP was characterized by a lower Ts/Tm and C31-homohopane22S/(22S + 22R) and a higher Pr/nC17 compared to coal TOGP, while the aromatic parameter methyl dibenzothiophene ratio (MDR) exhibited coaly shale TOGP was higher than coaly shale SOGP than coaly TOGP than coaly SOGP, and coal trimethylnaphthalene ratio (TNR) was lower than coaly shale TNR. Thus, we established oil generation processes and discriminative plates. In this way, we distinguished the differences between oil generation parent maceral, oil generation time, and oil production of coaly source rocks, and therefore, we provided important support for the evaluation, prediction, and exploration of oil resources from global ancient coaly source rocks.

Lacustrine source rocks have a significant oil potential and contribute to 95 % of oil reserves in China's offshore areas, Nature of these rocks is related to climate and structure and they are commonly heterogeneous. Mechanism of organic matter accumulation in these rocks has been a matter of debate. Based on Rock-Eval pyrolysis, organic petrographic examinations, gas chromatography-mass spectrometry (GC-MS) analysis, and trace elements analysis, this paper illustrates the paleoclimate, tectonic activity, paleo-productivity, and preservation conditions recorded in high-quality source rocks of the Shanan Sag. The aim is to understand the controlling factors on the deposition of these source rocks. The results indicated that the organic matter of source rocks in middle segment of the third member of the Shahejie Formation (Es3m) was mainly from phytoplankton (average content = 52.2 %), the development of source rocks was controlled by high paleo-productivity. The primary productivity was low during the period of the first and second members of the Shahejie Formation (Es1-2), and the high gammacerane index, and low Pr/Ph ratios indicated that the source rocks were mostly controlled by a good reduction environment with high salinity. The source rocks of the third member of the Dongying Formation (Ed3) were characterized by high terrestrial materials (average exinite content = 62 %) and low to moderate Pr/ Ph ratios, which indicated the source rocks were affected by both paleo-productivity and preservation environment. A productivity-controlling model in Es3m was established along with a co-controlling model of productivity and preservation in Ed3, which was largely developed under the background of a warm-humid climate and strong depression-controlled fault activity. The development model of source rock in Es1-2 can be concluded as a preservation model under a hot arid climate and weak fault activity. The development model of source rock in Es1-2 can be concluded as a preservation model under a hot arid climate and weak fault activity.

An integration of outcrop observations,as well as data from drilling,logging,and seismic surveys in an oilfield is applied to analyze the filling types and filling cycle assemblages of karst caves associated with paleokarst buried rivers;accordingly,the filling sequences and patterns of the paleokarst buried rivers,as well as the discussion on their petroleum geological implications.The results show that the Ordovician buried-river karst caves with a filling rate of 89.9%in the Tahe oilfield,are predominantly filled with sandy mudstones and collapse breccias.These karst caves host multiple combination cycles featuring coarse-grained lower parts and fine-grained upper parts,which can be classified into polycyclic sedimentary assemblages and polycyclic collapse-sedimentary assemblages for filling.The former is distributed in the karst slope's lower reaches of flat landform,where wells with lost circulation and stringers account for small and high proportions,respectively.In contrast,the latter is situated in the karst slope's upper reaches featuring landform of great drops,where wells with lost circulation are of high proportion together with multiple high-yielding wells.The following conclusions can be reached through analysis:(1)The tortuous spatial structure of buried rivers,combined with their strong runoff transport capacity,facilitate the filling of large amounts of karst detrital materials,resulting in an extremely high filling rate;(2)The seasonal fluctuations in the phreatic surface lead to the formation of cyclic and comparable fillings.This,coupled with water erosion and tectonic activities,gives rise to multi-phase collapses of karst caves.Consequently,polycyclic collapse-sedimentary filling assemblages are formed in the upper reaches,with unfilled spaces developed;(3)The relatively closed underground environment supersaturated with calcium carbonate,results in severe calcareous cementation of fillings,decreasing the intergranular porosity;(4)The unfilled spaces serve as the major targets with potential for oil and gas exploitation.

为明确济阳坳陷下古生界碳酸盐岩地层断裂结构对油气成藏的控制作用,文中选取青州云门山地区碳酸盐岩露头断裂进行野外地质考察,利用岩心、野外露头、分析化验等资料,对碳酸盐岩地层断裂结构及其控藏作用进行系统研究,建立了多期方解石胶结、泥质充填和"三元"断裂结构,揭示了 3种断裂结构差异化控藏作用.研究认为:多期方解石胶结断裂结构对油气具有垂向输导和横向封堵双重作用,控制油气沿大型油源断层两侧断块圈闭选择性成藏;泥质充填断裂结构对潜山油气成藏具有明显的封堵作用,控制油气在不同的断层-不整合油藏中大规模富集成藏;"三元"断裂结构具有破碎带和裂缝带输导、角砾岩带封堵的双重作用,控制油气主要沿油气来源方向的断层下盘呈梳状富集成藏.断裂结构差异化控藏模式将为济阳坳陷下古生界碳酸盐岩潜山油气勘探提供理论依据.

Paleoenvironmental information is better preserved in carbonate concretions. In this study, carbonate concretions in the Cretaceous Nenjiang shale, Songliao Basin, were examined to determine whether molecular fossils reflective of the paleoenvironment were better preserved at these sites. Organic and inorganic geochemical characteristics of the concretions and surrounding rocks were analyzed using a series of techniques, including SEM, LA-ICP-MS, GC-MS-MS, and GC-IRMS. The concretions are composed of high content microcrystalline dolomite. The δ13Ccarb and δ18Ocarb values of the concretionary dolomite were significantly higher than those of the surrounding rocks. The dolomite show enrichment in the LREEs and have a negative Eu anomaly. The concretion biomarkers showed distribution characteristics similar to those of surrounding rocks. This suggested that the molecular fossils preserved in concretions were mainly inherited from surrounding rocks. However, the concretions contained more C27 sterane and hopanes, with the hopane/sterane ratio being significantly higher than that of surrounding rocks (1.49 v. 0.86). Moreover, the relative content of 2-methylhopane was 2.4–6.6 times that of the surrounding rocks. This indicated changes in the biological equilibrium of source organisms within and outside the concretions. It was possible that the unstable organic matter at the core increased the bacterial concentration and activity inside the concretions. Both the hydrogen index and biomarker-derived indicators implied that the transformation of organic matter in concretions was minimized when compared with their host rock. The isotope δ13C16-30 was 1‰–3‰ more prevalent in individual N-alkane hydrocarbons in the concretions than in surrounding rocks, likely owing to differences in lithology, bacterial action, and degree of weathering. The study concluded that carbonate concretions could preserve molecular fossils better than the surrounding rocks, and the in-depth organic geochemical analysis of concretions could provide a valuable reference for research into early life forms.

The Carboniferous-Permian was an important period for the formation of coal mines and coaly source rocks across the world. Controlled by the paleoclimate, Cathaysia flora, and transitional sedimentary environment of the delta, the Early Permian Shanxi Formation in the Huanghua Depression formed several layers of coal and coaly source rocks that can be explored in the whole depression. However, the development regularity and distribution prediction of high-quality coaly source rocks are still not well understood. The coaly source rocks of the Shanxi Formation in the Huanghua Depression were taken as the research object. With the determination and analysis of organic carbon content, rock pyrolysis, and vitrinite reflectance, we found that the organic matter abundance (i.e., TOC which changed from 20.3 % to 80.0 %), hydrocarbon generation potential (i.e., S1 + S2 which varied from 7.82 mg/g to 208.81 mg/g), and kerogen types (mainly type II2) of the coal were better than carbonaceous mudstone and coaly shale. Maceral component identification indicated that coal and carbonaceous mudstone had more liptinite (i.e. cutinite and sporinite)and hydrogen-rich vitrinite, while coaly shale was mainly composed of hydrogen-poor vitrinite and a small amount of liptinite. The analysis of the ratios of major and trace elements, normal alkanes, and isoparaffin suggested that the paleo-water salinity of coal and carbonaceous mudstone deposition was more than that of part coaly shale. Revealed by the weak reduction of their depositional environment, the development of high-quality coal and carbonaceous mudstone was mostly controlled by the input of oil- and gas-prone organic matter. The formation of high-quality coaly shale was chiefly dominated by a strong reduction environment with an insignificant amount of organic matter input. The formation model of high-quality coaly source rocks was established. This model can be used to predict the distribution of coal mines and coaly source rocks in the Huanghua Depression and Bohai Bay Basin.

微生物降解是浅层原油常见的次生变化,为了简单快捷地确定原油遭受生物降解的程度,提出一种利用饱和烃降解率划分原油生物降解级别的方法.该方法利用生物降解原油的饱和烃色谱图会出现"UCM"峰的特点,在同一比例尺下读取"UCM"峰面积和残留饱和烃包络面积,计算饱和烃降解率,并依此将原油降解级别划分为10个等级.利用该方法对LDW坳陷32个原油样品饱和烃降解率进行计算,并对生物降解级别进行划分.结果表明:LDW坳陷原油生物降解级别分布在1～7级,且不同构造位置原油降解级别存在差异,同一构造不同深度原油的降解级别也不尽相同;总体上中南部(D36-1构造以南)原油降解级别较高,Z25-1构造及其以北原油降解级别较低,原油降解级别随油藏埋藏深度变浅而升高,反映浅埋原油易于降解的特征;该方法步骤简单,且具有分析周期短、成本低、精度高的优点,为定量划分原油生物降解级别提供了高效方法.

济阳坳陷已在沙四段和沙三段获得页岩油勘探开发重要突破.在沙一段页岩层系虽然也获得了工业油流,但目前对沙一段页岩油的认识整体薄弱,其是否能作为济阳坳陷页岩油长远发展的下一领域尚不明晰.以济阳坳陷渤南洼陷沙一段为例,采用生烃物理模拟、分析测试、测井评价及资源评价等方法,研究了沙一段的生油能力、含油特征及页岩油资源潜力.结果显示:渤南洼陷沙一段页岩层系为一套优质源岩,具有有机质类型好、丰度高、碳酸盐含量高的特点;热模拟实验表明,沙一段页岩生烃门槛较低,生烃高峰靠前,约在镜质体反射率(Ro)=0.4％时进入生烃门限,在Ro=0.65％时开始进入生烃高峰,这与沙一段优质的有机质组分和碳酸盐的催化作用有关;含油性评价表明,沙一段生油量(约41.5亿吨)中约有35％滞留在页岩层系中,可溶烃含量(S1)＞2 mg/g、含油饱满程度(OSI)＞120mg/g时有游离油存在,且S1值越高,游离油所占比例越大.预测沙一段页岩层系游离油资源量约4.7亿吨,沙一下亚段游离油含量和含油饱满程度均高于上亚段,认为Y21断阶带沙一下亚段是渤南洼陷页岩油勘探的有利区.

为了揭示黄河口凹陷不同层段烃源岩供烃潜力,利用8000余组总有机碳、岩石热解、氯仿沥青"A"、有机元素、镜质体反射率等数据,对12个层段的有机质丰度、有机质类型和成熟度进行分析对比.研究发现,沙三中、沙三下亚段有机质丰度最高,达到极好烃源岩标准;沙一段、沙二段、东三段、沙三上为好烃源岩;沙四-孔店组、东二下亚段、东一段为中等—差烃源岩,东二上亚段、明化镇组与馆陶组未达到烃源岩标准.黄河口凹陷烃源岩有机质类型总体偏腐殖型.其中,沙三中、沙三下、沙一—二段、东三段相对较好,沙三上、沙四-孔店组、东二上、东二下有机质类型普遍较差,主要是II2—III型.沙四-孔店组烃源岩整体处于成熟—高成熟演化阶段,沙河街组烃源岩整体处于生油窗范围,东营组烃源岩处于未熟—低熟阶段.综合有机质丰度、有机质类型和成熟度指标认为,沙三中、沙三下烃源岩最优,沙一二段、沙三上、沙四-孔店组烃源岩次之,东营组还不能大规模供烃.

The paleokarst system is one of the main carbonate reservoirs, which can form important super-large oil fields. There are many typical paleokarst reservoirs in the Tarim Basin Ordovician strata, mainly composed of caves, vugs, and fractures. Due to the deep burial depth and strong heterogeneity, qualitative identifying the different scale fracture-vuggy reservoirs from the tight limestone around the wellbore is a real challenge in the industrial community. In this paper, machine learning methods were used to classify electrofacies. Firstly, core samples and electrical imaging logging of the paleokarst reservoirs are observed in detail and a core-electrical imaging chart was established. Secondly, conventional logging data was optimized and preprocessed for data mining, using Principal Component Analysis (PCA) algorithm and K-means algorithm. High-resolution electrical imaging logging was chosen as a constraint to recognize electrofacies, and an electrofacies-lithology database was established. Thirdly, based on the electrofacies-lithology database, Linear Discriminant Analysis (LDA) algorithm was used to build an electrofacies prediction model, which can automatically identify the electrofacies in carbonate strata, with a coincidence rate of 92.2%. Finally, the model was used to quantitatively recognize paleokarst reservoirs and their distributions. The electrofacies machine learning workflow proposed in this paper could be used in Tarim Basin and other similar paleokarst reservoirs, which can improve exploration efficiency and save economic cost.

Based on a large number of drilling, logging, seismic and production data, the differential structures of karst zone and hydrocarbon distribution in different paleogeomorphic units of the Tahe area, Tarim Basin, are discussed by analyzing the karst drainages and flowing channels. The karst paleogeomorphy of Ordovician in Tahe area is composed of watershed, karst valley and karst basin. The watershed has epikarst zone of 57.8 m thick on average and vadose karst zone of 115.2 m thick on average with dense faults, fractures and medium—small fracture-caves, and 76.5% of wells in this area have cumulative production of more than 5×104 t per well. The karst valleys have epikarst zone, vadose karst zone and runoff karst zone, with an average thickness of 14.6, 26.4 and 132.6 m respectively. In the runoff karst zone, the caves of subsurface river are mostly filled by fine sediment, with a filling rate up to 86.8%, and 84.9% of wells in this area have cumulative production of less than 2×104 t per well. The karst basin has no karst zone, but only fault—karst reservoirs in local fault zones, which are up to 600 m thick and closely developed within 1 km around faults. Different karst landforms have different water flowing pattern, forming different karst zone structures and resulting in differential distribution of oil and gas. The watershed has been on the direction of oil and gas migration, so medium—small sized connected fracture-caves in this area have high filling degree of oil and gas, and most wells in this area have high production. Most caves in subsurface river are filled due to strong sedimentation and transportation of the river, so the subsurface river sediment has low hydrocarbon abundance and more low production oil wells. The faults linking source rock are not only the water channels but also the oil-gas migration pathways, where the karst fractures and caves provide huge reservoir space for oil and gas accumulation.

Although various coaly source rocks widely developed in the Carboniferous-Permian (C-P) of the Bohai Bay Basin, their geochemical characteristics and hydrocarbon generation potential are poorly understood. This study aims to discriminate the contribution of hydrocarbon generation from different C-P coaly source rocks and clarify the differences within generated oils using organic geochemistry, organic petrology, and thermal simulation experiments. The coaly source rocks containt coal clarain and durain, carbonaceous shale, and shale deposited in deltaic and lagoonal environment. The results indicated that clarain, durain, and carbonaceous shale exhibited higher hydrogen index and liquid-gas hydrocarbon yields than lagoonal and deltaic shales, which was mainly associated with the concentrations of sporinite, cutinite, and hydrogen-rich collodetrinite. Aliphatic hydrocarbons originated from coal and carbonaceous shale presented lower Ts/(Ts + Tm), Gα/17α(H)21β(H)-C30 hopane, 18α(H)-oleanane/17α(H)21β(H)-C30 hopane ratios, and higher 17β(H)21α(H)-C30 Morane/17α(H)21β (H)-C30 hopane than deltaic lagoonal shales. Parameters of aromatic hydrocarbons generated from five lithologies of coaly source rocks trended as clear group distribution, e.g., clarain and durain showing lower MNR, DBT/Fluorene (F) ratios and higher DBF/F ratio than coaly shales. The distinct descending trend of hydrocarbon potential is obtained from clarain, durain, carbonaceous shale to lagoonal and deltaic shales, implying dominated the petroleum and natural gas supplement from coal and carbonaceous shale. The difference between aliphatic and aromatic hydrocarbons provides a significant contribution to analyze the generic relationship between coaly source rock and lacustrine shale. Our results illustrate the importance of coaly source rocks for the in-depth oil-gas exploration of the Bohai Bay Basin and understanding hydrocarbon generation potential of source rocks in coal bearing strata.

The mechanisms of lacustrine organic-rich shale formation have attracted attention due to its association with global shale oil and shale gas exploration.Samples of general-quality and excellent-quality source rocks,and oil shale from the Beibu Gulf Basin were analyzed to investigate their organic geochemistry,palynofacies,and trace elements.Hydrocarbon potential was higher in the oil shale(29.79 mg/g)than in the general-quality source rock(3.82 mg/g),and its kerogen type was Ⅰ-Ⅱ2.Hydrogen-rich liptinite(cutinite and sporinite)components derived from terrigenous higher plants provided most of the hy-drocarbon potential of excellent-quality source rock and oil shale.Under the influence of depression-controlling fault activity,a deeper subsidence center promotes the deposition of excellent-quality source rock and oil shale in brackish-hypoxic bottom water.A shallower subsidence center,due to subsag-controlling fault activity,promotes the formation of excellent-quality source rock under fresh-brackish and weak oxidation-weak reducing conditions.The local uplift and shallow-slope led to the formation of general-quality source rock,under freshwater weak-oxidation conditions.A model was established for organic matter(OM)accumulation in organic-rich shales,accounting for fault activity,terrigenous hydrogen-rich OM,and the preservation conditions,to predict the development of excellent-quality source rock from areas with low levels of exploration.

将岩溶地质学与地质地球物理资料相结合,对塔河地区奥陶系碳酸盐岩岩溶斜坡分水岭的组成和缝洞结构进行解剖.在岩溶水系划分的基础上,重点分析S48和S74分水岭的结构组成和缝洞发育特征,剖析出断块石林、断槽溶谷和断坡溶丘3个组成部分.结果表明:岩溶期走滑挤压背景下发育的正花状构造(地貌高带)起着分水岭作用,将塔北岩溶斜坡划分成多个岩溶流域;断块石林受断层推举处于分水岭高部位(奥陶系与巴楚组突变接触),其中裂缝和缝洞复合体发育,岩溶储层可达116 m;断槽溶谷为断层切割低部位,除裂缝/缝洞复合体发育外,奥陶系内发育4类驻水洞、槽谷内发育巨型角砾遮挡洞穴以及岩溶期堆积物,岩溶储层厚度可达136 m;断坡溶丘位于分水岭翼部,裂缝和缝洞复合体组成的岩溶储层厚度一般小于50 m.断块石林和断槽溶谷油气富集,62％的油井单井累积产油量超过20×104 t,而断坡溶丘76％的油井单井累积产油量小于10×104 t.

Based on a large number of geological and geophysical data, the formation, fracture-caves types and hydrocarbon distribution of hoodoo-upland on the Ordovician karst slope in the Tahe area, Tarim Basin, are discussed by analyzing faults and strata thickness. The hoodoo-upland was made of high peaks and narrow valleys in the Ordovician karst slope during the Early Hercynian karst period, which were distributed along the NNE positive flower structure and had inherited evolution. The fault-fractures and fracture-vugs complex were extremely developed, with a thickness of 100 m. The cumulative oil production of 60% oil wells was more than 20×104 t per well in the hoodoo-upland, where the residual thickness of the Ordovician Yingshan Formation was greater than karst depressions. Caves formed by the shelter of collapsed breccias were developed in the valleys. They were 1.6 to 13.5 m high, with a filling rate of 51.6%. The positive flower structure under the settings of strike-slip compression controlled the early formation of the hoodoo-upland on the karst slope, resulting in the differences of drainage distribution and karstification. Compared with the water-rich karst valley, the hoodoo-upland with lean water suffered weaker karstification, had thicker residual stratum, and was higher in terrain. In rainy season, the meteoric water flew and corrode along the cracks, forming a complex network of fractures and caves. Combined with inherited uplift and the effective match of the NNE deep faults, oil and gas continuously charged into the reservoir space in the upland, forming the hoodoo fracture-cave reservoir with vertically quasi continuous distribution, high hydrocarbon abundance and high production.

在岩溶缝洞储层精细描述过程中,利用钻井校正地震的方法恢复岩溶末期的岩溶地貌,发现塔河油田奥陶系岩溶区内东西两侧发育由走滑断裂形成的地貌高带(分水岭),其间为一向南开口的喇叭口状洼地,南接岩溶盆地;利用钻井、测井与地震综合解释方法,发现洼地北部较陡(坡度为2.9°左右)、南部较缓(坡度为1.5°),发育由众多支流汇聚的2条岩溶水系,西侧一条在北部以地表河为主,在南部转入地下河,东面一条地表河与地下河交替发育,由3段地表河和2段地下河组成.由于强烈的侵蚀与溶蚀作用,形成了不同规模及充填物的5种地表河,但多数地表河内没有发现河流砂岩充填,只有岩溶湖泥灰岩沉积;而地下河溶洞内充填了大量的砂岩和泥岩,成为重要的油气储层.地表河原本是有砂泥沉积的,当下游发育地下河时,洪水把原有的砂泥岩冲入地下河,形成了溶洞砂泥岩沉积,除少数下游地表河残留砂泥岩外,塔河地区奥陶系岩溶地表河基本不存在砂质储层.

岩溶储层极为复杂、研究难度大,采用注重控制因素和形成过程的岩溶相分析可以提供更可靠的地质依据.通过塔河油田主体区奥陶系岩溶储层精细描述,发现该区在岩溶期的塔北隆起挤压走滑背景下,呈一系列河流—落水洞—岩溶湖形成的峰丘—高地、残丘—谷地、岩溶湖泊—洼地等岩溶相带:形成了S74(NE向)和S48(近SN向)2个带状峰丘—高地,这两个峰丘—高地将研究区与其他岩溶相带系统隔离开来,河流穿过峰丘—高地以瀑布形式进入喇叭口状残丘—谷地,部分河流通过落水洞进入渗流岩溶带和径流岩溶带形成驻水洞和地下河,部分流入下游的岩溶湖泊—洼地.通过分析峰丘—高地和残丘—谷地岩溶相带的断层—裂缝特征、缝洞溶蚀作用、缝洞充填等岩溶相标志,并引入湖南现代岩溶相带形成过程分析,提出了岩溶相带模式,阐明了地表河与地下河及其缝洞储集空间的分布规律.研究结果为碳酸盐岩缝洞型储层预测评价和地质建模提供了岩溶地质依据.

依据大量地质和地球物理资料,从构造形变的角度出发,采用井震结合、层面追踪及三维建模的方法,对塔河油田海西运动早期岩溶地貌的形成过程进行研究.结果 发现,塔河油田古生界可分为2个形变构造层,一个是寒武系—奥陶系形变构造层,呈平缓背斜构造;另一个为石炭系—二叠系形变构造层,呈褶皱链式构造披覆于奥陶系之上.印模法不适用于塔河油田岩溶地貌的恢复,基于现今奥陶系顶面构造形态,建立构造等效圆弧曲线方程,依据不同构造阶段挤压形变压缩率,采用等弧长积分法,有效去除了岩溶期后的构造形变量,恢复了岩溶期地貌形态.海西运动早期,塔河油田奥陶系岩溶地貌北高南低,西倾东翘,其构造幅度为现今构造幅度的70％,具继承性演化特征,2个高耸带状峰丘高地与其间低缓箕状河丘谷地以及南部平坦开阔岩溶湖,共同构成了一个完整、独立的岩溶系统.

为了明确塔河油田海西早期构造演化及其对岩溶缝洞形成与油气运聚的影响,利用最新的叠前深度偏移数据及大量钻井资料,对塔河地区构造特征、水系分布、缝洞类型进行研究.通过层面追踪、精细相干技术,明确了研究区断层发育特征和构造差异演化历程,采用三维雕刻技术,刻画了地下河溶洞及中小型缝洞空间分布,多因素叠合分析认为研究区奥陶系海西早期存在差异抬升,控制着岩溶水系和缝洞分布.研究结果表明:海西早期Ⅰ幕,塔河地区呈南北向隆起,北高南低,鹰山组残余地层南厚北薄;海西早期Ⅱ幕,北西向挤压应力继续作用,构造脊线向东旋转,形成北东向鼻隆,同时鼻隆轴部发育北北东向低角度逆冲断层F3,使研究区发生差异演化;塔河六、七区沿F3断层逆冲抬升形成断鼻型峰丘高地,而塔河十、十二区相对下降,呈相对低缓的岩溶斜坡-洼地;斜坡-洼地区沉积了近200m巴楚组合岩溶角砾砂砾岩层(C1b1),岩溶水系和地下河溶洞广泛发育,油井累产小于1×104 t;峰丘高地区未沉积C1b1段,断裂与缝洞复合体密集发育,油井累产大于20×104t.因此,差异抬升形成的峰丘高地成为了岩溶斜坡上的分水岭,控制着岩溶水系的分布,使地表河与地下河围绕分水岭呈裙带式分布于斜坡-洼地区;峰丘高地与深大断裂发育区成为油气运聚优势区,斜坡-洼地中的深大断裂带可形成油气“甜点”.