Marine carbonate rocks in China are characterized by aging, developing in small-scale cratons and locating in the lower tectonic layer of superimposed basins. Reservoir genesis and distribution are among the many scientific problems in hydrocarbon exploration. This paper summarizes three innovative achievements made by the project team of the Key Laboratory of Carbonate Reservoir in the past five years in the field of marine carbonate sedimentary reservoir research in China as follows: (1) based on the analysis of tectonic-lithophase paleogeography of the Sinian-Cambrian, Changxing Formation-Feixianguan Formation in Sichuan Basin, it is found that the intra-platform rifts in small-scale craton were generally developed, and thus the carbonate platform sedimentary models of bi-margin ＆ bi-shoal were established. This discovery reveals that the source rocks and large-scale reservoirs can also develop in the intra-platform, which provides a theoretical basis for the exploration field expansion from the margin to the internal of the platform, and it was confirmed by the discovery of the Anyue gas field; (2) based on the exploration practice of karst reservoirs in the Tarim Basin, innovations in the genesis of karst reservoirs and the type ＆ distribution of karst reservoirs of intra-carbonate rocks broke the traditional view that the karst reservoirs mainly develope in the buried hills. This view extends the exploration realm from the buried hill areas to intra-carbonate rocks areas, and it was confirmed by the discovery of Harahatang and Shunbei oilfield on the south slope of North Tarim Basin; (3) the old and deep-buried marine carbonate reservoirs are still facie-controlled and the pores are more inherited from pre-buried stage than modificated in buried stage, which laid the foundation for the scale and predicatability for deep-buried and ancient marine carbonate reservoirs, which promote the exploration values of these reservoirs. This view was confirmed by the hydrocarbon exploration practice in Tarim and Sichuan Basins. Reef-shoal(mound) facies, evaporite tidal flats, sequence boundaries, exposure surfaces and unconformities, paleo-uplifts and fault systems control the distribution of high-quality and large-scale reservoirs of deep-buried and ancient marine carbonates. These understandings not only have important theoretical significance for the development of carbonate sedimentary reservoir discipline, but also provide basis for the expansion of exploration field.

Considering the strong heterogeneity, the multiple-scale characterization and evaluation of carbonate reservoir has been studied in order to meet the needs in different stages of exploration and development. Lower Triassic Feixianguan Formation in Chuandong-Exi area, Middle Ordovician Yijianfang Formation in Tarim Basin, and Lower Cambrian Longwangmiao Formation in Sichuan Basin were taken as examples to clarify the advances of reservoir-modeling, heterogeneity characterization and evaluation at macro scale, reservoir scale, and micro scale. With the advance in digital data collection of flat outcrop, the reservoir modeling and characterization at macro scale mainly reveals the distribution of reservoir and non-reservoir geo-bodies, and the reservoir distribution in sequence stratigraphy framework, which could constrain the seismic reservoir prediction in the early stage of exploration. By means of importing the digitized outcrop modeling, the reservoir modeling and characterization at reservoir scale is able to characterize the heterogeneity in single reservoir geo-body, and present the distribution pattern of flow unit and barriers, which is important in the prediction of effective reservoir, oil and/or gas distribution in reservoir, and well deployment. With the advance in logging and seismic templates of permeable and barrier layers, reservoir characterization at micro scale can reveal the differences in pore-throat structure and their controls on percolation feature in flow units as well as the productivity and recovery.

Tectonic-lithofacies paleogeography is the foundation of the evaluation for source-reservoir-cap and reservoir-forming assemblage, which plays a significant role in oil and gas exploration. However, because of the limited data and recognition, the existing facies maps of major marine basins in China can not meet the needs of oil and gas exploration in deep marine carbonate rocks. Based on the new drilling and seismic data, the lithofacies recognition technology was used to restore the marine tectonic-lithofacies paleogeography of Tarim Basin, Sichuan Basin and Ordos Basin. It is concluded that: (1) the tectonic paleogeography of China's marine carbonate platform in small craton is characterized with the alternation of uplift and depression, and uplift controlling reservoir and depression controlling source rocks; (2) tectonic-lithofacies paleogeography is characterized with multiple platform margins, multiple shoal zones and multiple platform basins; (3) tectonic-lithofacies paleogeography plays an important role in the early dolomitization and the range and reconstruction degree of karstification, thus controlling the distribution of reservoir; (4) multiple margin platform model is established and double-shoal sedimentary model of gentle slope is improved, which reveals that there are many favorable reservoir-forming assemblages in the marine carbonate platform of China. The research results deepen the understanding of the common characteristics of China's marine carbonate platform in small craton, and provide theoretical support for oil and gas exploration of deep marine carbonate rocks.

After nearly ten years of construction and development, the CNPC Key Laboratory of Carbonate Reservoir has preliminarily developed five technical series, including rock composition & structure analysis, reservoir geochemical experiment, pore formation and distribution simulation, reservoir geological modeling and seismic reservoir prediction based on reservoir geological model, which offers a one-stop solution for carbonate sedimentary & reservoir research. This paper focuses on the technical connotation, technical progress and application of two technical series of rock composition & structure analysis and reservoir geochemical experiment. The analysis of rock composition & structure is the most basic work of carbonate sedimentary & reservoir and provides a means for further study of sedimentary & reservoir. The reservoir geochemical experiment mainly includes isotope and element geochemical detection, which has been widely applied in the research of carbonate reservoir genesis and distribution. The laser-ablation U-Pb isotopic dating, carbonate clumped isotope analysis, laser carbon and oxygen isotope online analysis and laser trace-rare earth element mapping are the core techniques of the reservoir geochemical experiment developed in recent years, reflecting technical development trend from whole rock to in-site to mapping in reservoir geochemistry.

Carbonate rock dissolution refers to the process and results of interaction between flowing erosive fluid and carbonate rocks. Carbonate rock dissolution may take place at surface, burial and deep burial conditions. Dissolution simulation of carbonate rock is to reproduce the process and results of carbonate rock dissolution under simulating formation environment, which is an important method to study the favorable conditions and distribution rules of scale dissolution of carbonate reservoir. Since 1930s, many carbonate dissolution experiments have been conducted by researchers in China and abroad. The technology of dissolution simulation of carbonate rock mainly goes through three stages: surface dissolution of rock under relative low temperature and low pressure, surface dissolution of rock under high temperature and high pressure, and internal dissolution of rock under high temperature and high pressure. The CNPC key laboratory of carbonate reservoir has designed the high temperature ＆ high pressure dissolution dynamics simulation apparatus, and developed the carbonate dissolution simulation technology which consists of functions of rock internal dissolution, rock surface dissolution, visual and analysis in situ under high temperature and high pressure. Experiments of temperature window and pore evolution pattern of carbonate rock burial dissolution were done by using the high temperature ＆ high pressure dissolution dynamic simulation apparatus. The results of experiments with high salinities fluid show that the dissolution quantity of carbonate rock has the characteristics of slow declining- slow rising fast declining. Because of the action of two opposite ionic effects in high-salinities fluid, 80~110 ℃ is the favorable temperature window for carbonate rock burial dissolution. The comparative dissolution simulations of five types carbonate rocks of interparticle pore, intercrystalline pore, dissolved pore - dissolved vug, oolite moldic pore and growth-framework pore, indicate that the connecting pore is the prerequisite and favorable place for the occurrence of buried dissolution, and the difference of internal fabric of carbonate rocks will further increase the complexity of reservoir space in the combination of pores, vugs, and fractures.

In view of the characteristics of carbonate reservoir with strong heterogeneity and complex plane distribution, based on the recognition that the distribution of carbonate reservoir is mainly controlled by large-scale unconformity surface, interlayer karst surface, fault system, reef-shoal facies belt and gypsum dolomite facies belt and other geological elements, the carbonate reservoir prediction technologies are developed with the integration of geology, logging and seismic on the basis of reservoir geological model and the calibration of reservoir logging identification and evaluation chart, with the identification of platform type/lithofacies, sequence boundary, karst reservoir, fault system, reef-shoal body and dolomite body as the core. These technologies have been applied to the prediction of the karst reservoir of Ordovician buried hill in west Lungu, inner fault-karst reservoir of Ordovician buried hill in Halahatang oilfield of Tarim Basin, the reef-shoal reservoir of Sinian-Cambrian, the crystalline dolomite reservoir of the Middle Permian Qixia Formation in Sichuan Basin, and dolomite weathering crust reservoir of the upper assemblage of Ordovician Majiagou Formation in Ordos Basin，and the coincidence rate of reservoir prediction increase by more than 20,.

Based on the observation of typical outcrops, cores and petrographic thin sections, combined with the experimental analysis data, the lithofacies palaeogeography, reservoir characteristics and their main controlling factors of the Cambrian Xixiangchi Formation in Sichuan Basin were studied. The results show that: (1) The Xixiangchi Formation is developed in the rimmed carbonate platform, and the Sichuan Basin is located in the interior of the limited platform as a whole, with the high-energy shoal facies developing on both sides of the Liangping-Chongqing platform depression; (2) The effective reservoirs are mainly developed in the middle and upper part of Xixiangchi Formation, dominated by grain dolomite, crystalline dolomite and algae dolomite. The reservoir spaces are consisted of dissolution pore, intergranular pore, intercrystalline pore and fracture, with porosity mostly at the range of 2,～5, and the average of 3.46,. (3) The formation and distribution of reservoirs are controlled by sedimentary facies, penecontemporaneous dissolution and supergene karstification. Reservoirs are mainly developed in the higher part of paleogeomorphology, and in the upper part of upward-shallowing cycle of sea water, and near the pinchout line of Ordovician. It is predicted that the areas of Hechuan-Guang'an and Nanchuan-Shizhu, as the high parts of palaeogeomorphology at the both sides of Liangping-Chongqing platform depression, are the favorable shoal reservoir zones, and Xichong-Guang'an-Tongnan area is the favorable karst reservoir zone. It is concluded that the Xichong-Guang'an area is the main target zone of natural gas exploration in the future.

Based on the results of outcrop geological survey, core and slice observation, geochemical analysis, and reservoir simulation experiment, the lithofacies paleogeography, and the characteristics, origin, distribution of dolomite reservoir of the Cambrian Longwangmiao Formation in Sichuan Basin are analyzed. As a result, five conclusions are drawn: (1) The Cambrian Longwangmiao Formation could be divided into upper and lower sections in the Sichuan Basin, recording the climate change from humid to arid. In addition, the carbonate distally steepened ramp sedimentary models were established. (2) The granular shoals, the developing basis of the dolomite reservoir, are mainly distributed in the shallow ramp of the upper section of the Longwangmiao Formation. (3) Moreover, the contemporaneous dissolution, controlled by the exposure surface, is a critical factor for the development of granular shoal reservoir in the Longwangmiao Formation. (4) The dissolution vugs are not only extensively distributed, but also successively developed along the contemporaneous pore zones. (5) The granular shoals are superimposed in many stages in Yanting-Anyue-Weiyuan area, which are located in the high part of paleogeomorphology and developed buried dissolution, so it is a favorable area for exploration. Moreover, the granular shoals widely distributed in the whole basin are the potential exploration targets.

Based on the detailed analysis of the lithologic characteristics, sedimentary structure, sedimentary assemblage and facies sequence of field outcrops and drilling data, six types of sedimentary facies can be identified in Guanwushan Formation of Middle Devonian in Western Sichuan. From west to east, basin-slope facies, platform margin facies, open-confined platform facies, and tidal flat facies are developed successively. The distribution of sedimentary facies in northwest Sichuan is obviously controlled by Devonian syndepositional faults, with the characteristics of migration from west to east, and the evolution of platform margin from reef to shoal. Influenced by paleo-island, the distribution and evolution of sedimentary facies in southwest Sichuan is controlled by both syndepositional faults and barrier islands. Sedimentation controls the development of carbonate reservoirs of Guanwushan Formation obviously, which is mainly manifested in that sedimentation controls the type of carbonate reservoirs and the development degree of primary pores, the facies-controlled penecontemporaneous dissolution controlled by sedimentary cycles improves the primary pores, and facies distribution controlled by sedimentary evolution controls the plane distribution of carbonate reservoirs.

Based on the data of drilling, outcrop, logging, seismic and micro -area multi-parameter experimental analysis obtained in recent years, the key geological problems of the Permian Qixia Formation in sichuan basin are systematically analyzed and the following recognitions is obtained: (1) The sedimentation of Qixia Formation is controlled by the residual geomorphology of Middle Sichuan paleouplift, in which the shallow ramp is developed in most areas of paleouplift. The eastern margin of the paleouplift appears as a shape of"S", and gradually evolves into a medium-deep ramp towards the southeast. The geomorphology of the western margin of the paleouplift is relatively the highest, which is the basis for the development of the platform margin. (2)In the middle-late Qixia period, there exists a right-leaning "L" type slightly rimmed platform margin in western Sichuan, which extends to Guangyuan area in northeast and Emeishan area in southwest. The platform margin transforms into a broad sea sharply in the west and a carbonate ramp gradually in the east. (3) As the main reservoir rock of Qixia Formation, crystalline dolomite is formed gradually under the penecontemporaneous magnesium-rich fluid infiltration and reflux, and is finalized after adjustment and transformation in a buried environment.(4)High quality dolomite reservoirs are controlled by sedimentary facies, sequence interfaces, micro-paleogeomorphology and other factors, among which the thick crystalline dolomite layers are mainly distributed in the Guangyuan-Jiangyou and Ya'an-Leshan areas in western Sichuan Basin, and the medium-thin crystalline dolomite layers are mainly distributed in the Nanchong-Moxi-Gaoshiti areas in central Sichuan Basin.

Based on data of outcrop, drilling core, logging, thin section and other macro and micro data, the characteristics of sedimentary facies, reservoir types, reservoir-controlling factors and reservoir distribution patterns of the Perimian Maokou Formation are systematically studied in Sichuan Basin. The author obtains the understanding as follows: (1) The sedimentary pattern of Maokou Formation is influenced by the NW-SE faults formed by Emei taphrogenesis, but not by Caledonian paleo-uplift. (2) Carbonate ramp, slope and basin are three main facies in Maokou Formation. The high-energy shoal of high-stand system tract developed in shallow ramp in the middle-late period of Maokou is the most favorable reservoir sedimentary facies. (3) Two types of reservoir such as hole-pore dolomite reservoir and karst fractured-vuggy limestone reservoir are developed in Maokou Formation. The high-energy bioclastic shoal is the material basis for reservoirs of Maokou Formation. Early dolomization is the key factor for the preserving of dolomite reservoir, tectonic movement and paleo-karstification are important conditions of reservoir development. (4) Dolomite reservoir is mainly distributed in the Ya'an-Leshan and the Yanting-Guang'an areas. Karst fractured-vuggy limestone reservoirs are distributed in the whole basin, but the Luzhou-Kaijiang uplift is the most developed area.

Up to now，no large-scale oil or gas field group has been found in Leikoupo Formation of Middle Triassic in Sichuan Basin. The key problem is that the formation mechanism and distribution law of reservoirs are not well understood. Starting from the division and correlation of sequence stratigraphy, the stratigraphic distribution, sedimentation and reservoir characteristics of the Middle Triassic are systematically sorted out and analyzed by using the latest oil and gas exploration results and abundant basic data. The results show that: (1) the Middle Triassic Tianjingshan Formation (also known as "the Leikoupo Formation Member 5") exists in the basin, which is one of the important favorable exploration strata in the Middle Triassic; (2) microbial carbonate rock is an important type of carbonate rock of Leikoupo Formation, which has the potential acting as large-scale effective reservoir; (3) dolomitization and karstification in paracontemporaneous period and karstification in supergene stage are the main controlling factors of reservoir pore forming in Leikoupo Formation, and the acid diagenetic environment in early burial period, dissolution and structural fractures in burial period are the key factors for pore maintenance, improvement and transformation; (4) the distribution zone of weathering crust karst around the paleouplift, and the distribution zone of the microbial rock and granular shoal reformed by paracontemporaneous and supergene karstification are favorable reservoir development zones.

Well Luntan 1 in the Lunnan area of the Tarim Basin has made a major breakthrough in the dolomites of the Lower Cambrian platform margin zone at a depth of more than 8 000 m, which proves that the Cambrian platform margin zone has developed high-quality source-reservoir-cap assemblages and is an important oil and gas exploration field in the deep layers of the Tarim Basin. Based on petrology, isotope stratigraphic comparison and seismic facies analysis, it is believed that the Cambrian platform margin belt in Lunnan area has experienced the sedimentary evolution process from the early carbonate gentle slope to the middle-late rimmed platform, forming multiple sets of high quality Cambrian subsalt source-reservoir-caprock assemblage. The Lower Cambrian Yuertus Formation was developed in mud-rich middle gentle slope outer zone-outer gentle slope in relatively deep water, and a set source rock of 20-30 m was developed in the formation. The Lower Cambrian Xiaoerbulak Formation was developed in middle gentle slope outer zone with limes depositing on it, and tidal flats and granular shoal dolomite reservoirs developed locally in high structural positions. In the Wusonggeer period of Early Cambrian, 8-10 km wide mound-shoal reservoir was developed in weak-rimmed margin. During the Middle Cambrian, strong-rimmed platform margin with a width of 4-5 km was developed; 5-8 km wide argillaceous dolomite of gypsum dolomite flat-argillaceous dolomite flat facies and 10-15 km wide gypsum-salt rock of gypsum salt lake-salt lake facies were developed in platform interior, which formed two kinds of high quality cap rock. It is pointed out that the most realistic exploration field in the Lunnan area is the reservoir-cap assemblage of the granular shoal reservoir in weak-rimmed platform margin and behind the reef of Wusonggeer Formation and gypsum-salt cap rock of Middle Cambrian. It is worth exploring for the reservoir-cap assemblage of the inter-salt granular shoal in the Middle Cambrian Shayilik Formation. The dolomite strata in the upper part of the Xiaoerbulak Formation in the high part of the paleostructure still have exploration potential.

The Ordovician in Gucheng area of Tarim Basin has shown good exploration potential in recent years. Based on observation of the core and petrographic thin section, analysis of cathodoluminescence, inclusion and bitumen reflectance of more than 10 Ordovician exploration wells, and interpretation of seismic data in Gucheng area, and combined with regional research results, the reservoir forming and hydrocarbon accumulating conditions of Ordovician carbonate rocks in Gucheng area are systematically analyzed. The results show that: (1) Paleostructure-geofluid processes is an important factor controlling the development of granular dolomite reservoir and hydrocarbon accumulation in the lower member of Yingshan Formation and Penglaiba Formation of Lower Ordovician. (2) Tectonic thermal events after Permian played a key role in adjustment and transformation of oil and gas accumulation. Under the influence of magmatic hydrothermal activity, large-scale oil cracking of primary reservoir occurred in Caledonian-Early Hercynian period, forming crude oil-cracked gas reservoirs and residual paleo reservoirs. (3) The formation and evolution of Ordovician oil and gas reservoirs have experienced three stages, including the formation of primary oil and gas reservoirs, the destruction of ancient reservoirs and the generation of oil-cracked gas, and the adjustment, destruction and reformation of gas reservoirs. It is pointed out that the west and the north of Gucheng low uplift are favorable for oil and gas exploration because of good combination conditions of source, reservoir and caprock, and less influence of faults and magmatic intrusion.

The genetic model and the controlling factor on the development of Ordovician dolomite reservoir are not clear, which seriously restricted the effective prediction of high quality dolomite reservoir, and the further exploration and discovery of the natural gas in the western margin of Ordos Basin. Controlled by the evolution of Helan depression in Early Ordovician, the western margin of Ordos Basin is located in a gentle slope or the weakly-rimmed platform of open sea with a certain barring of the inner gentle slope, middle gentle slope and the platform edge belt, where carbonate rocks extensively developed. The observation of rock and thin section shows that the Ordovician dolomites in the western margin of the basin are mainly composed of granular dolomite with clear residual particle structure, and crystalline dolomite including micritic-powder crystalline dolomite, coarse powder crystalline dolomite, powder-fine crystalline dolomite, fine crystalline dolomite, fine-medium crystalline dolomite, medium-coarse crystalline dolomite. The geochemical analysis of dolomite shows that the oxygen isotope δ18O values of the Ordovician dolomite in the western margin of the basin are generally negative, the carbon isotopes δ13C values are more positive, the trace elements are characterized with low Na, K and higher Fe content, and the strontium isotope 87Sr/86Sr values are obviously larger than those of the seawater in the same period, and the REE distribution curve is right deviation model of negative Eu anomaly. The cathodoluminescence shows orange, dark red and red, and the homogenization temperature of inclusions is generally high. According to comprehensive analysis of petrological characteristics, regional tectonic and sedimentary evolution, climatic environment and geochemical characteristics, the Ordovician micritic-powder crystalline dolomite in the western margin of the basin was formed by evaporation pump dolomitization in the paracontemporaneous period, and the fine crystalline-granular dolomite was formed by reflux infiltration dolomitization in shallow burial period. The inner gentle slope, middle gentle slope and the granular shoals on the edge of the platform have high primary porosity, which are more easily dolomitization, and the distribution of the Ordovician dolomite is discontinuous and uneven. After dolomitization, the primary pore of granular shoal in contemporaneous period was preserved because of the strong anti-compacting ability of dolomite. Later, further dissolution expanded to form the most important reservoir space in the Ordovician dolomite reservoir.

In view of the problems that the lack of a systematic microbialites classification, the uncertain of facies significance of different microbialites types and the lack of sedimentary models, this paper made a series of detailed study on petrology and rock assemblage sequence of two Proterozoic profiles and three Phanerozoic profiles in Tarim, Sichuan and Ordos Basins, acquiring three achievements and understanding: (1) Establish a new microbialites classification based on structure scale and morphological characteristics which is more systematic. (2) Make out the facies significance of the microbialites: laminated carbonate is the dominant type below the storm wave base; foamed and crumbed thrombolites, and domed, tapered, columnar stromatolites are mostly developed between storm wave base and normal wave base; wavy stromatolites are mostly developed between normal wave base and average low tidal base; and the lime-mud mound, sheet-like and mound-like microbial carbonates mainly exist in tidal flat environment over the average low tidal base. (3) Establish two microbialite sedimentary models for ramp sedimentary system and rimmed sedimentary system. These understandings are of great significance for reconstruction of lithofacies palaeogeography and prediction of reservoirs distribution of microbial carbonate.

The Ordovician pre-salt dolomite reservoir is an important replacement field for natural gas exploration in Ordos Basin. Based on drilling core, thin section, physical analysis, geochemical characteristics and other related information, the characteristics, genesis and distribution of the Ordovician pre-salt dolomite reservoir are systematically studied by using the method of multi-parameter analysis in micro-region. The results showed that: (1)The granular shoal dolomite reservoir and microbial dolomite reservoir are mainly developed in the Ordovician pre-salt. The reservoir lithology of granular shoal dolomite is arenaceous dolomite, oolitic dolomite and very fine-fine crystalline dolomite, the pore space is composed of dissolved pores, intergranular pores, intercrystal (dissolved) pores and fractures, and the average porosity is 6.04,. The lithology of microbial dolomite is thrombolite dolomite, the pore space is composed of dissolved pores, dissolved vugs and micro-fractures, and the average porosity is 5.64,. (2)The pores of the Ordovician pre-salt reservoir inherited the primary pores of granular shoal and microbial dolomite which suffering from the dissolution, dolomitization, the mineral filling of gypsum, salt, quartz, finely-medium crystalline dolomite and calcite. (3)It is predicted that the favorable reservoir is mainly distributed in the central paleo-uplift, the Hengshan uplift belt and the low uplift zone of Wushenqi depression.

The Middle Cambrian Zhangxia Formation is an important target strata for Cambrian oil and gas exploration. Through detailed field outcrop survey, core and petrographic thin section observation and experimental analysis, the characteristics, genesis and main controlling factors of reservoir of Zhangxia Formation are analyzed and studied, and favorable reservoir development areas are predicted. The results show that: (1) Zhangxia Formation mainly develops two types of reservoirs: platform margin oolitic shoal dolomite and intra-platform oolitic shoal dolomite. (2) The cumulative thickness of oolitic shoal in platform margin zone is concentrated in 50~300 m, and the average diameter of oolitic is 1.25 mm. The reservoir space of oolitic dolomite in platform margin is dominated by dissolution pores, intergranular dissolution pores and intergranular (dissolution) pores, and the average logging porosity and permeability are 2.0, and 0.038×10-3 μm2 respectively. (3) The thickness of intra-platform oolitic shoal ranges from 50 m to 120 m, and the average diameter of oolitic is 0.85 mm. The reservoir space of oolitic dolomite in the platform is dominated by dissolution pores and intergranular dissolution pores, and the average logging porosity and permeability are 3.3, and 2.787 ×10-3 μm2 respectively. (4) The reservoir of Zhangxia Formation is controlled by oolitic shoal facies, dolomitization and third / fourth-order sequence boundary. The favorable reservoir of platform margin is developed in the oolitic dolomite strata in the middle and upper part of fourth-order regressive sequence, and the favorable reservoir of platform interior is developed in the oolitic dolomite strata below the unconformity surface at the top of Cambrian. On this basis, two large-scale favorable reservoir development areas of Qishan-Xunyi area in platform margin and Longdong area in platform interior are predicted.