Effect of Sand Body Enrichment Under the Restriction of a Tectonic Transfer Zone: A Case Study on the Pinghu Formation in the Kongqueting Region on the Pinghu Slope

LI Junjie, HOU Guowei, QIN Lanzhi, XIE Jingjing, and JIANG Xue

CNOOC (China) Co., Ltd., Shanghai Company, Shanghai 200030, China

Abstract Results of long-term explorations in the Kongqueting region, located in an East China Sea depression, suggest that the strong fault activity during the sedimentary period of the Pinghu formation significantly influenced the development of the sedimentary system. However, the aggregation and enrichment of the sand body under a tectonic background has become a problem that requires an immediate solution. Considering research outcomes of previous studies, this study used three-dimensional seismic and logging data to identify Y- or H-type and the en echelon distribution patterns of the fault plane, as well as identify the locations wherein the fault growth index value is greater than 1 in the study region, indicating the tectonic background of the fault transfer zone in the region. Second, the development type of the fault transfer zone was studied, and the sand body enrichment site was identified based on seismic inversion data and the development position of the fault transfer point. This helps clarify the evolution of sedimentary facies of the Pinghu formation combined with the sedimentary environment of the braided-river delta. Finally, after summarizing the coupling relationship between the synsedimentary fault systems and the sand body enrichment patterns, three sand-control models were determined, namely, the flexural-parallel, the en echelon collinear, and the torsional-reformed superimposed transfer zones. The findings of this study lay a foundation for the subsequent search of tectonic lithologic oil and gas reservoirs.

Key words synsedimentary fault; paleogeomorphology; structural transfer zone; sand body distribution; Kongqueting

1 Introduction

Recent studies on sedimentary basins have unraveled the importance of structural paleogeomorphology on the sedimentation process (Chen, 2007). In the rift basins that have undergone active tectonic movement, synsedimentary fault systems, which occur by altering the positive and negative geomorphological features, affect the space available for sedimentation (accommodation), the drainage direction of the paleo-water system, the sand body distribution, and the development of sedimentary facies zones (Xieet al., 2015). The middle-east basins in China are marked by rift-depression types, a result of early rift basins undergoing lengthy transformations into depression basins.For basins in this rift-depression transition stage, the movements in the dominant fault are reduced, the rift effect slows down, the depression hotspot moves from the peripheral toward the center of the basin, and the micropaleogeomorphology becomes a prominent factor in determining the sand and sedimentary facies as a result of the secondary and concealed fault transfer zone (Wanget al.,2018).

Dahlstrom first proposed the concept of tectonic transfer zones in the 1970s to analyze the nappe formed in the thrust compressional deformation system (Dahlstromet al.,1970). In the late 1980s, scholars around the globe gradually began to pay more attention to this field. Among them,Scott and Rosendahl (1989) presented a detailed elaboration of four types of regulatory transfer zones in their research of the North Viking graben based on the research outcome of the East African rift. In the early 1990s, Morleyet al. (1990) successfully introduced research results on transfer zones in China (Scott and Rosendahl, 1989; Morleyet al., 1990). Domestic scholars soon became interested in transfer zones as well. For example, Tianet al. (2013)discussed the significant constraint imposed by the Dongying Sag tectonic transfer zone on the distribution of sedimentary sand bodies and the formation of oil and gas traps.Liu and Wu (2016) classified tectonic transfer zones into 15 types according to the dips of normal faults and the planar combination relationships among the dips. Zhouet al. (2019a) provided a detailed explanation of the influence exerted by the tectonic structural transfer zone of the Pearl River Mouth Basin on fan deltas and the beach-bar sedimentary system (Tianet al., 2013; Suet al., 2014; Zhouet al., 2019a). These studies show the process by which tectonic transfer zones control different types of sedimentary sand bodies, such as deltas, sand bars, or low-laying fans. These sand bodies later became favorable sites for the development of large-scale reservoirs, thus aiding the discovery of large offshore gas fields, such as those of the Pearl River Mouth Basin and Bohai Bay Basin.

Located in a western slope zone inside an East China Sea depression, Pinghu slope covers a study area of 5000 km2and accounts for more than 50% of the depression’s reserve to date, thereby making it one of the key oil and gas reservoirs in the East China Sea. Among previous studies on the region’s tectonic features and sedimentary system,the work of Caiet al. (2014) identified three stages in the Paleogene structural transfer. Zhouet al. (2019b) found that the Pinghu formation sedimentary transfer exerts a certain degree of influence on the oil and gas abundance of the region. Houet al. (2019) identified the developmental features of the shallow-braided river delta that have formed resulting from the synsedimentary transfer in the Pinghu formation in the Kongqueting region of Pinghu slope. Liuet al. (2020) described the Mesozoic and Cenozoic structural features of a Xihu Sag depression and explicitly identified the mature nature of the regulatory transfer faults during the sedimentation stage of the Pinghu formation of the Kongqueting region (Caiet al., 2014; Houet al., 2019;Zhouet al., 2019b; Liuet al., 2020). These studies on the Pinghu formation in the Kongqueting region, however, focused on the structural transfer feature and regional sediment distribution; they did not investigate the effects of the synsedimentary transfer on the sand and sedimentary facies. Thus, the current study employs three-dimensional(3D) seismic data and observation wells to evaluate the Pinghu strata in the rift-depression transition stage and to offer a systemic explanation of the effects of the synsedimentary transfer on sand body enrichment.

2 Geological Background and Tectonic Evolution

2.1 Regional Geological Background

The Kongqueting region is located in a sag in the tectonic zone of the Pinghu slope in the East China Sea. It is adjacent to the sea reef uplift in the west, reaching the west subsag in the east and Hangzhou tectonic zone in the north.This area is also bounded by the Tiantai tectonic zone in the south. The study area is about 24 km long and 15 km wide and has an overall area size of about 360 km2(Fig.1).Drilled wells revealed that the tertiary stratum of the sag reached a thickness of 5000 m. The Cenozoic strata in the basin are fully developed, and the Paleogene strata that developed in series from the bottom all the way to the top include the following Baoshi formation, Pinghu formation,Huagang formation, Longjing formation, Yuquan formation,Liulang formation, Santan formation, and the Donghai formation of Quaternary (Caiet al., 2014; Zhouet al., 2019c).During this period, the sag experienced five large-scale tectonic movements. Among these, the Yuquan and Huagang tectonic movements divided the sag from the bottom to top into three tectonic layers, namely, rift, depression,and regional subsidence. The Baoshi formation developed in the rift period, the Pinghu formation developed during the fault-depression transition period, and the Huagang formation developed during the depression period (Fig.2).

2.2 Tectonic Evolution Stage

Fig.1 Tectonic location and outline of the Pinghu formation in the Kongqueting region.

The Yuquan tectonic movement that occurred at the end of the Eocene period is one of the most critical tectonic movements of the sag to which Kongqueting belongs. It divides the regional tectonic evolution into two periods(i.e., rift and depression) and has significantly influenced the evolution of the Paleogene stratum (Chen, 1998). During the Paleocene period, the subduction of the Indian Ocean Plate caused the continental margin creep of the Eurasian Plate, resulting in a near east-westward tensile stress, and the study area entered the sedimentation stage of the rift period (Geet al., 2014). Subsequently, under the continuous action of tensile stress, the eastside of the main fault that developed in the NE-NNE direction continued to deposit strata. The Baoshi formation and members 5 and 6 of the Pinghu formation were deposited during the early Eocene,i.e., when the Baoshi formation and early Pinghu rift system developed into the peak stage. In the middle and late Eocene, the rifting gradually weakened, the Pinghu formation entered the rift-depression period, and members 1 - 4 of the Pinghu formation were formed by deposition. During the Oligocene period,i.e., the Huagang formation period, the subduction of the Pacific plate in the NWW direction caused the continental edge of the Eurasian plate to end creeping; it also led to weakened tensile stress and the entry of the basin into the depression stage(Huet al., 2010), as shown in Fig.2.

3 Identification and Types of Structural Transfer Zones

To facilitate the sand and sedimentary facies analysis,the Kongqueting region is divided into ‘high’, ‘middle’,and ‘low’ zones from west to east (Fig.3). The Pinghu formation in the Kongqueting region was mainly affected by continued torque and tension, and was dominated by the development of forwarding multistage tensional normal faults, with gradually weakening fault activity rate (Zhouet al., 2014). Weak tensile stress in the NE-SW direction is superimposed on the NWW-SEE regional tensile stress field. Consequently, the faults that developed in the separate north and south segments during the early Eocene were gradually connected in the central Kongqueting region in the middle and late Eocene, thereby forming a fault transfer zone in which an en echelon torsional normal fault developed (Fig.4).

Fig.2 Characteristics of the Paleogene stratigraphic development in the Kongqueting region.

Fig.3 Seismic profile of the Kongqueting region.

Under the background of this tectonic stress, this study proposes three identification marks of the fault transfer zone for the study area based on the transfer zone identification method proposed by many scholars (Dahlstromet al., 1970; Gibbs, 1984, 1989; Xuet al., 1996; Zhaoet al.,2000). These three identification marks include the following. First, the synsedimentary fault plane must present an en echelon, a feather-like or diverging distribution pattern, and prominent bending (Fig.5) (Qiet al., 2019). Second, the growth index of fault in some locations must be greater than 1. A synsedimentary fault F3 in the middle Pinghu formation, located in the central part of the study area, was taken as an example. The seismic reflection interface between T34 and T32 was selected to calculate -from south to north - the ratios of the thickness difference between T34 and T32 of the descending plate with those between T34 and T32 of the ascending plate. The locus in which the ratio has a value ranging from 1 - 1.1 is considered the development site of the fault transfer point (Table 1). The third identification mark is the differential expression of tectonic styles. The tectonic styles of forward fault, bifurcation torsion, flower-like torsion, torsional transition fault type and torsional remodeling type were identified on the post-superimposed seismic profile(Fig.6). These tectonic styles are described as below.

a) Forward fault type: This showed an almost straight line extension in the plane, while in the vertical profile, it was controlled by a tensional-tension fault cutting the basement. The stratum on one side of the descending plate of the fault had a certain dip back commonly seen in the high in the high zone of the Kongqueting region.

Fig.4 Eocene coherence slices in the Kongqueting region: A, early Eocene; B, middle and late Eocene.

Fig.5 Identifying features of the Kongqueting well K-4 transfer zone.

Fig.6 Tectonic transfer types of the Pinghu formation in the Kongqueting region.

b) Bifurcation torsion (simple Y-type): This showed a Y-type in the plane, while in the vertical profile, it was controlled by a tensional-tension fault cutting the basement.Here a reverse regulating fault was formed on the side of the descending plate of the fault. Most of them developed in the high zone of the Kongqueting region.

Table 1 Calculation of fault growth index in the middle Pinghu formation

c) Flower-like torsion (complex Y-type): There was an en echelon in the plane, which was controlled by a tensile fault cutting the basement. Here, multiple forward and reverse regulating faults were formed on the descending plate of the fault in vertical profile. Such type was developed in the middle zone of the Kongqueting region.

d) Torsional transition fault: This showed an H-shape in the plane between two parallel faults cutting the basement.Here, a transition regulating fault was derived in the vertical profile.

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e) Torsional remodeling: This also showed a Y-type style in the plane, while in the vertical profile, the relatively ancient reverse fault was inactive in the later stage, and a new reverse fault with an oblique strike was generated on top. This and the torsional transition fault type are most typical in the low zone of the Kongqueting region.

The identification of the above types of structural transition zones in the study area is mainly due to the fact that the formation of the transition zones is essentially due to the segmented growth of faults. At an early stage, faults approach one another without coming in contact. In the middle stage, two faults approach and begin to interact,and yet, without obvious contact, they remain in a state of‘soft touch’. In the end stage, the surface of the contact dismantles owing to tectonic stresses, thus creating a new fault and entering the stage of ‘solid contact’. During this process, these ‘contact points’ become the development sites for the tectonic transfer zones (Shiet al., 2003).

The growing faults have an en echelon distribution on the horizontal plane as well as branched Y- or H-types on the vertical plane. These features can help scientists accurately identify the development sites. Furthermore, in the abovementioned sites, greater accuracy in identifying the transfer point can be achieved by calculating the fault growth index.

Three types of synsedimentary fault transition systems were established in the study area based on the abovementioned identifying features. Their features are presented below.

1) The parallel transfer zone refers to the transition system formed by the combination of two parallel or nearly parallel faults, showing a stepwise graben-like feature in the tectonic style (Fig.7). This type of transfer zone is typically found in the Kongqueting K-1 well block.

2) The collinear transfer zone refers to a fault transition system formed by two faults with fundamentally similar trending. These move toward each other following a straight or nearly straight line, before finally ‘hard connecting’into one fault (Fig.7). These transition faults are developed in the middle and low zones of the Kongqueting region.

3) The superimposed transfer zone refers to a tectonic transition system, wherein two faults are disconnected but have a certain degree of superposition on a plane, thus mutually influencing each other’s displacement. The most significant example of this is the K-5 well block (Fig.7).

3 Fault-Sand Coupling and the Evolution of Sedimentary Facies

3.1 Paleogeomorphology Features of the Pinghu Formation

Fig.7 Three tectonic transition systems of the Pinghu formation in the Kongqueting region.

The fault transition system developed in the Pinghu formation controls and influences the topography and geomorphology features of the study area in varying degrees.On the basis of the visual display of high-resolution 3D seismic data, the paleogeomorphology map of the Pinghu formation in the corresponding period is obtained. This was done by computing the seismic interpretation results of the bottom boundary of four sequences from T40 to T30 after restoration. Paleogeographic pattern analysis can identify the positive (uplift, salient) and negative (gully, depression) paleogeomorphology units and sedimentary unloading areas (Zhang, 2010).

Fig.8 Paleogeomorphology map of the Pinghu formation in the Kongqueting region. A, early stage; B, middle stage; C, late stage.

3.2 Sand Body Distribution Characteristics Under the Control of Transfer Zones

The synsedimentary paleogeomorphology controlled the drainage of the water system and the convergence of sand bodies (Zhouet al., 2014). This is a relatively effective technical method to fully use the inversion data volume to calculate the sand-to-ground ratio, which can be used in studying the distribution of the sand body under the background of lacking wells in the sea (Houet al., 2019). Using seismic lithology analysis, preprocessing drilling and seismic data can help determine the threshold of sandstone and mudstoneVp/Vs. Next, we obtained the number of sampling points below the threshold in the inversion data and the total number of sampling points (Fig.9). The ratio of the two refers to the sand-to-ground ratio of the study area. At the same time, six large backbone synsedimentary faults with large-scale plane development in the study area were selected. For each fault, the fault growth index was calculated, as previously described before, with 10 as the interval, marking the corresponding position on the plane.In this way, the fault growth index graph was obtained(Fig.9). Finally, we established the influence of tectonic transfer zone on the accumulation of sedimentary sand bodies and development of facies belts through a comprehensive comparison of the sand-to-ground ratio, paleogeomorphology, and fault growth index map of each period.

Fig.9 Relationship between the lithology of the Pinghu formation in the Kongqueting region and the ratio of the pand s-wave velocities.

Intense fault activities are observed in the early stage of the Pinghu formation. The high zone is dominated by parallel transfer zone, and the middle and low zones are dominated by superimposed transfer zone. The development of transfer zones dictates the formation of alternating depressions and uplifts, as well as a paleogeomorphology with local flexures (Fig.8A). From the retrieved sand-toground ratio map of this period, the paleo-water system entering from the west converges into the two depressions located north and south of the paleo-nose uplift, carrying sand bodies with it (the sand bodies haveVp/Vsthreshold value of below 1.7 and are color coded in yellow to red).This process happensviathe fault transfer point (local low point) in the parallel transfer zone. The K-3 well, which is located close to the fault transfer point and on a microgeomorphological uplift, features sand bodies with coarse grain size but small thickness. These sand bodies accumulate into fans on slopes. And the K-2 well near the fault transfer point is located on a micro-geomorphological low-lying terrain and features thick sand bodies with coarse grain size. These sand bodies develop into small low-lying fans. In comparison, the K-1 and K-4 wells that are distant from the fault transfer point show the low enrichment of sand bodies (Fig.10A). This period is marked by the sedimentation at the braided-river delta front, which is controlled jointly by tide and rivers. In the study area,the braided-river channels in the south flow eastward past the transfer point toward the depression. In contrast, the flexural geomorphology in the north directs the subaqueous distributary channels with terrigenous particles into the depression, thus forming limited-grown frontal lobes of subaqueous fans (Fig.11A).

The middle stage of the Pinghu formation features medium-intensity fault activities. Development in the parallel transfer zone of the high zone continued from the previous stage. The middle zone consisted mainly of the collinear transfer zone, and the low zone consisted of the transfer zone, which controlled the paleogeomorphology and made the terrain more even (Fig.8B). The height difference between the ascending and descending plates of the fault decreased, and the transfer point occurred at a different location. Along with the large-scale and rapid rise of the water body, the frontal sand bodies of the braidedriver delta gradually contracted and became concentrated on the paleo-nose uplifts formed during earlier periods.The K-3 well in the high zone, located close to the fault transfer point and on a paleogeomorphological uplift, became enriched with thin layers of fine-grain sandstone.Thus, the parallel transfer zone dictated the development of the front subaqueous fans along the long axis of the fault. Meanwhile, the K-4 well in the middle zone, located near the fault transfer point and in a depression, became enriched with thick sand bodies. The collinear transfer zone directed the concentrated development of small, lowlying fans in the low-lying areas. The low zone, in turn,was affected by the deepening water body. The microgeomorphology developed from the tectonic transfer zone played a shielding role in the synsedimentary period and controlled the development of isolated compound sand bars in the east of the K-5 well block (Figs.10B and 11B).

In the late stage of the Pinghu formation, the faulting activity was further weakened, and the palaeogeomorphology of broad and gentle slope was controlled by synsedimentary faulting system (Fig.8C). The sand-control effect of parallel and collinear transfer zones developed in the middle and high zones was also weakened significantly compared with the earlier stages. The superimposed transfer zone of the low zone mainly functioned to guide the flow of the water system. The K-4 and K-5 wells of the middle zone, located close to the fault transfer points and in a depression, became enriched with multiple sets of thick, medium-grain sandstone. The development of frontal subaqueous fans was also observed. The K-1 and K-3 wells of the high zone, with their location near the fault transfer points but on an uplift, became less enriched with sand bodies compared to the K-4 and K-5 wells. The development of fans on slopes and bars in the river channels was observed on the river delta of the braided river (Figs.10C and 11C, respectively).

3.3 Distribution Characteristics of the Sedimentary Facies of the Pinghu Formation

Fig.10 Sand-to-ground ratio and fault growth index in the Pinghu formation. A, early stage; B, middle stage; C, late stage.

Based on the comprehensive judgment of core, trace,well-logging, seismic, and geochemical facies, it can be assessed that the sedimentary period of the Pinghu formation consisted of shallow water braided-river delta (Houet al., 2019). Under such an ocean-land interaction background, tidal flat deposits, braided channel deposits, and interdistributary bay deposits can be identified through cores. Based on the single well facies, it was further determined that the water of the Pinghu formation rose first and then fell; here, the sedimentary sand bodies showed the characteristics of regressive deposition and progressive deposition (Fig.12). The sedimentary period of the Pinghu formation in the Kongqueting region generally consisted of the shallow-braided river delta, with the water level rising first and then falling. In the early stage of the Pinghu formation, the braided-river delta was deposited under the background of the tide-river joint control. Then,the sand body in the channel and frontal subaqueous fans respectively formed the braided-river delta plain and front frameworks. The fault system of the parallel transfer zone,which was developed in this period, controlled the middle and high zones in the study area to form flexural microgeomorphology. In turn, this led to the braided channel being introduced from the west to join the northern depression through the fault transfer point, eventually forming the subaqueous fans of the braided-river delta front, as shown in Fig.11A.

Large-scale flooding was also observed in the middle stage of the Pinghu formation. The deposition of the braided-river delta front affected by the tide was the main development mechanism. During this period, the collinear en echelon transfer zone and parallel transfer zone, which were formed and controlled by the synsedimentary fault,governed the westward extension of subaqueous fans along the direction of the fault stages. This westward extension was accompanied by fan edge contraction (Fig.12B). The seawater rapidly retreated, and the braided-river delta plain deposition developed during the late period of the Pinghu formation. Due to the weakening of fault activities in the K-5 well area, the torsional-reformed superimposed transfer zone that was developed and controlled by the synsedimentary fault mainly controlled the direction in which the braided water system entered the depression(Fig.12C).

4 Determination of the Sand-Control Models of the Pinghu Formation

On the basis of a comprehensive analysis and examination of the paleogeomorphology, fault transfer zone, and sedimentary facies, three types of sand-control models were identified in the Kongqueting region. These are described

Fig.11 Sedimentary facies plan of the Pinghu formation in the Kongqueting region in the early (A) and middle (B) stages.

Fig.11C Sedimentary facies plan of the Pinghu formation in the Kongqueting region in the late stage.below.

Fig.12 Sectional view of the sedimentary facies of the Pinghu formation in the Kongqueting region.

1) Sand-control model of the flexural-parallel transfer zone

This transfer zone sand-control model occurs mostly in the Kongqueting high zones of the early and middle Pinghu formation. Under the continuous NW-SEE regional tensile stress, the NE normal fault and the NW concealed fault jointly control the formation of the flexural geomorphology. Positive synsedimentary faults and northwestwardly concealed faults comprise the flexural geomorphology, thereby affecting the development site and growth direction of terrigenous particles. This also pushes the subaqueous fan at the braided-river delta front further toward the depression zone. Eventually, these fan formations became abundant in the flexural depressions, gradually developing into underwater sediments in the braided-river tributaries. Such terrigenous particles are of large sizes and volumes, but their distribution is confined to certain areas,rendering them unable to form large reservoirs. Their development sites are generally close to the hydrocarbonrich depressions where the source rock is mature and the reservoir and cap rocks are desirable. Thus, they have great potential for oil and gas explorations (Fig.13A).

2) Sand-control model of the en echelon collinear transfer zone

The superposition of NWW-SEE regional tensile stress and NE-SW weak tensile stress controls the development of the en echelon collinear transfer zone in the Kongqueting region. This type of the transfer zone developed in the middle zone plays two primary functions. On the one hand, it facilitates the transportation of the water system from the high zone; on the other hand, it facilitates local sand gathering and accumulation, aiding the accumulation and deposition of sand bodies at low-lying regions of the fault descending plate. These sand bodies eventually develop into a composite body of sand bars and subaqueous distributary channels. This type of sedimentary sand body has a coarse grain size, high degree of thickness, and extends far and wide in the direction of transfer zone-controlled channel development. Furthermore, they are organically coupled with hydrocarbon-rich depressions and oil-source faults and could potentially give rise to various types of oil and gas reservoirs. Thus,the areas developing this type of sand-control model can serve as the key sites of future oil and gas explorations(Fig.13B).

Fig.13 Schematic of the sand-control models of faults in the Pinghu formation in the Kongqueting region.

3) Sand-control model of the torsional-reformed superimposed transfer zone

On the basis of a stress background that is similar to the echelon type collinear transition zone, the synsedimentary faults that gradually declined in the early north-south segment growth and the late period controlled the formation of the Peacaoting torsional transformation type overlay transition zone. Numerous sand transportation and control systems of the torsionally-remodeled superimposed transfer zone are developed in the middle and low zones of the study area. Parts of the fault descending plate with small vertical displacement overlap and superimpose each other in the fault system of this type of transfer zone. This leads to the formation of a water gathering channel that, in turn,guides the convergence of the paleo-water system eastward along these low-lying regions into the depression. This type of transfer zone is mainly involved in guiding the flow of the water system into the basin. However, its sand-control effect is not as good as the other two; thus, it holds a low potential for future oil and gas explorations (Fig.13C).

5 Conclusions

1) The Pinghu formation in the Kongqueting region on the Pinghu slope is in the fault-depression transition period. In this study, the development of the tectonic transfer zone in the study area was determined based on the identification of the en echelon plane features, the calculation of the fault growth index, and the differentiation of the tectonic styles.

2) During the Pinghu formation in the Kongqueting region on the Pinghu slope, tectonic activity grafault combinations developed, which continued to control and influence the distinct paleogeomorphology features.

3) During the fault-depression transition period, the fault transfer zone and paleogeomorphology controlled the distribution of the water system, the accumulation of the sand body, and the development of facies zones. Three sandcontrol models were formed in the study area, namely, the flexural-parallel transfer zone, the en echelon collinear transfer zone, and the torsional-reformed super-imposed transfer zone. Three models distinct features have been discussed, and the implications have been presented.

Acknowledgements

This work was supported by the National Science and Technology Major Project of China (No. 2016ZX05027-002-009), and the Science and Technology Project of the CNOOC, known as the ‘Research on Key Technologies of Exploration and Development in Western Xihu Sag’ (No.CNOOC-KJ 135 ZDXM 39 SH01).