Southeast Chongqing Research Articles

Sedimentary mode and reservoir genesis of dual grain banks at the Lower Cambrian Longwangmiao Fm carbonate ramp in the Sichuan Basin

The gas reservoir of the Lower Cambrian Longwangmiao Fm in the Sichuan Basin is a supergiant integral marine carbonate gas reservoir whose single scale is currently the largest in China. In order to figure out its sedimentary model and reservoir genesis, its geological structures and sedimentary settings and facies were analyzed comprehensively and the lithofacies paleographic map was plotted. It is revealed that the following sedimentary facies are successively developed in the Longwangmiao Fm from West Sichuan to Southeast Chongqing: diamictic tidal flat at the back ramp, grain bank (the upper bank) at the inner/shallow ramp – interbank sea (depression), deeper open bay at the platform depression of inner ramp → evaporative lagoon → evaporative tidal flat, tempestite at the middle ramp – barrier beach – mud mound beach (the lower bank), and outer ramp – basin. Accordingly, the specific sedimentary model of dual grain banks in the Longwangmiao Fm carbonate ramp was established as follows. Firstly, in this model, dual grain banks are symmetrically developed with Wanzhou–Yibin platform depression as the axis, on whose dual sides the paleohighs have shallow water bodies with strong energy. Compared with the classical model, the new one has a new upper bank which is developed around the paleohighs covering an area of about 8 × 104 km2. Secondly, the upper bank is large for its paleogeomorphology being located at the highest position with the strongest water energy during deposition. Therefore, it is prone to dolomitization and meteoric dissolution respectively during contemporaneous–penecontemporaneous hot-dry and hot-humid periods, and especially the Caledonian–Early Hercynian denudation wedge out tends to undergo post-supergene multiphase karstification. Therefore, quality reservoirs are more developed on scale. Thirdly, the intergranular pores and vermes moldic pores were dissolved and enlarged due to the multiphase atmospheric fresh water leaching, and together with tectonism, grain bank facies controlled multicyclic laminated–quasi-laminated, fracture-pore and cellular vuggy karst reservoirs were formed.

The pore size distribution and its relationship with shale gas capacity in organic-rich mudstone of Wufeng-Longmaxi Formations, Sichuan Basin, China

The pore size distribution for the 23 fresh outcrop shale samples collected from Shuanghe Town and Changning County, as well as the 14 core samples collected from the Qianqian 1 core well in southeast Chongqing, Sichuan Basin were investigated by means of low-pressure nitrogen adsorption. The main factors controlling pore development and gas accumulation in shales were discussed by integrating total organic carbon (TOC), mineralogy, and shale gas content. The results showed that open, slit-like, and parallel plate structure are major pore types that posses an average pore diameter of 3.76–8.53 nm; chiefly 2–30 nm for mesopores. The BET surface area and total pore volume are high in the Wufeng Formation and in the lower part of the Longmaxi Formation, and it's a bit lower in the upper part of the Longmaxi Formation. Consistent with the trends of TOC, that organic matter is the key controlling factor in the shale pore development. In addition, samples with higher content of clay minerals, but comparative TOC content have a larger specific surface area where clay mineral hosted pores are present. The Wufeng Formation and lower part of the Longmaxi Formation in the Sichuan Basin are preferred layers of shale reservoir fracturing due to high TOC, high rock brittleness, and high gas content.

Geological models of gas in place of the Longmaxi shale in Southeast Chongqing, South China

Gas-in-place (GIP) is one of the primary controlling factors in shale gas production, but studies examining GIP have been lacking for the Lower Silurian Longmaxi shale in South China. In the present study, a suite of Longmaxi shale samples was collected from an exploratory well in Southeast Chongqing, South China, and the adsorption parameters were fitted using a supercritical Dubinin-Radushkevich (SDR) model based on the high-pressure methane adsorption experiment data for the samples. The results show that the adsorbed phase density and the adsorbed gas capacity of the samples have a positive correlation with the content of total organic carbon (TOC) but a negative correlation with temperature. Combined with the geological characteristics of the Longmaxi shale in Southeast Chongqing, GIP models were constructed under three different fluid pressure conditions. The absolute adsorbed amount of the samples increases and later decreases with increasing depth with a maximum corresponding to depths between 800 and 1200 m. The fluid pressure coefficient has no obvious effect on the absolute adsorbed amount when burial depth is over 2000 m but controls the free gas content. Overpressure primarily increases the free gas content and thus increases the total gas content. The free gas content of the Longmaxi shale in the Pengshui Block is reduced to 47%–58% of that in the Fuling Block, which is the main reason for its low gas production. Further exploration of the Longmaxi Formation should be expanded to deeper burial shales in the eastern area of Southeast Chongqing.

Natural Fractures and Their Effects on Reservoir Reconstruction in Lower Cambrian Shale, Southeast Chongqing, China

Natural fractures in shale are important for the preservation and exploitation of shale gas. The classification of fracture types and characterization of system parameters would help to better evaluate reservoir properties. An evaluation of the relationship between natural fractures and hydraulic fractures may help to predict the effects of fracturing on reservoir properties and assist fracturing design. This study focuses on fractures in Lower Cambrian marine shale in southeast Chongqing, China. The fracture system is characterized in detail through observations and descriptions of several outcrops, cores, and thin sections. Hydraulic fracturing experiments were conducted using a large-size triaxial simulator, enabling us to discuss the effects of natural fractures on the creation of hydraulic fractures in a reservoir. The shale contains three primary fracture types: structural fractures, digenetic fractures, and abnormal pressure fractures. High-angle shear fractures (75°–90° from bedding) are the dominant type of seepage fractures observed in the study area. Three sets of tectonic fractures were formed during three tectonic movements. East–west fractures formed mainly in the Yanshanian. Hydraulic fracturing experiments indicated that the Lower Cambrian shale had a good level of reconstruction. The interference between natural fractures and hydraulic fractures has resulted in the segmentation. This study maybe have some reference for fracturing parameter design.

Depositional Settings and Enrichment Mechanism of Organic Matter of the Black Shales at the Bottom of Niutitang Formation, Lower Cambrian in Southeast Chongqing: A Case Study from Well Yuke 1

Acta Geologica Sinica - English EditionVolume 89, Issue s1 p. 287-287 Meeting AbstractsFree Access Depositional Settings and Enrichment Mechanism of Organic Matter of the Black Shales at the Bottom of Niutitang Formation, Lower Cambrian in Southeast Chongqing: A Case Study from Well Yuke 1 Wei XIA, Wei XIA State Key Laboratory of Geological Processes and Mineral Resources; School of Earth Science and Resources, China University of Geosciences, Beijing 100083 ChinaSearch for more papers by this authorBingsong YU, Corresponding Author Bingsong YU State Key Laboratory of Geological Processes and Mineral Resources; School of Earth Science and Resources, China University of Geosciences, Beijing 100083 ChinaCorresponding author. E-mail: yubs@cugb.edu.cnSearch for more papers by this authorMengdi SUN, Mengdi SUN State Key Laboratory of Geological Processes and Mineral Resources; School of Earth Science and Resources, China University of Geosciences, Beijing 100083 ChinaSearch for more papers by this author Wei XIA, Wei XIA State Key Laboratory of Geological Processes and Mineral Resources; School of Earth Science and Resources, China University of Geosciences, Beijing 100083 ChinaSearch for more papers by this authorBingsong YU, Corresponding Author Bingsong YU State Key Laboratory of Geological Processes and Mineral Resources; School of Earth Science and Resources, China University of Geosciences, Beijing 100083 ChinaCorresponding author. E-mail: yubs@cugb.edu.cnSearch for more papers by this authorMengdi SUN, Mengdi SUN State Key Laboratory of Geological Processes and Mineral Resources; School of Earth Science and Resources, China University of Geosciences, Beijing 100083 ChinaSearch for more papers by this author First published: 20 August 2015 https://doi.org/10.1111/1755-6724.12304_30Citations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume89, Issues1Special Issue: Meeting Abstracts: The 3rd Academic Conference on Unconventional Oil & Gas Accumulation and Exploration, Qingdao, China, 27 to 30, June 2015September 2015Pages 287-287 RelatedInformation

Organoporosity Evaluation of Shale: A Case Study of the Lower Silurian Longmaxi Shale in Southeast Chongqing

Organoporosity Evaluation of Shale: A Case Study of the Lower Silurian Longmaxi Shale in Southeast Chongqing

Evaluation Indexes for High Quality Shale Reservoir of Lower Silurian Longmaxi Formation in Southeast Chongqing

Evaluation Indexes for High Quality Shale Reservoir of Lower Silurian Longmaxi Formation in Southeast Chongqing

Characterization of Microscopic Pore Structures in Shale Gas Reservoirs of the Southeast Chongqing

Characterization of Microscopic Pore Structures in Shale Gas Reservoirs of the Southeast Chongqing

An investigation of body mass index distribution in couples with planned pregnancy in Chongqing

The incidences of overweight and obesity in planned pregnant women in Chongqing were 24.15% and 5.02%. Those living in southeast Chongqing, being old age, with primary school education, and unemployment are the key crowds and deserve health management in regard of overweight and obesity as well as reproduction. (Chin J Endocrinol Metab, 2015, 31: 243-244) Key words: Planned pregnancy; Overweight; Obesity

Organoporosity evaluation of shale: a case study of the Lower Silurian Longmaxi Shale in southeast Chongqing, China.

The organopores play an important role in determining total volume of hydrocarbons in shale gas reservoir. The Lower Silurian Longmaxi Shale in southeast Chongqing was selected as a case to confirm the contribution of organopores (microscale and nanoscale pores within organic matters in shale) formed by hydrocarbon generation to total volume of hydrocarbons in shale gas reservoir. Using the material balance principle combined with chemical kinetics methods, an evaluation model of organoporosity for shale gas reservoirs was established. The results indicate that there are four important model parameters to consider when evaluating organoporosity in shale: the original organic carbon (w(TOC0)), the original hydrogen index (I H0), the transformation ratio of generated hydrocarbon (F(R o)), and the organopore correction coefficient (C). The organoporosity of the Lower Silurian Longmaxi Shale in the Py1 well is from 0.20 to 2.76%, and the average value is 1.25%. The organoporosity variation trends and the residual organic carbon of Longmaxi Shale are consistent in section. The residual organic carbon is indicative of the relative levels of organoporosity, while the samples are in the same shale reservoirs with similar buried depths.

The Impact on the Voltage Fluctuation of Wind Power Integrated Separately in Chongqing Distribution Network

Recently, the development of Chinese wind power generation has formally entered the strategic transformation stage with the combination of large-scale integrated exploitation and distributed access exploitation. It is suitable to adopt distribution access mode due to the characteristics of Chongqings planning wind farm including small generation capacity and distributed location. However, considering that most of planning wind farms are located in the mountain area of northeast and southeast Chongqing with the large-scale geographic area and small load request and the distribution networks are relatively weak, there may be remarkable effect on quality of electric energy even though the distribution access mode is adopted. In this paper, aiming at the voltage fluctuation of access point, the relationships among variables affecting the voltage fluctuation is analyzed, then taking two planning wind farms in northeast and southeast Chongqing respectively as examples, the effects of voltage fluctuation caused by different access points are calculated and analyzed in order to get the allowed maximum capacity of wind farms fitting national standards. In the end, the proposals relevant to the development of wind power and contribution of distribution network are submitted according to the case results.

Fracture development in Paleozoic shale of Chongqing area (South China). Part two: Numerical simulation of tectonic stress field and prediction of fractures distribution

A tectonics sedimentation evolution has been researched in Southeast Chongqing, and the reasonable Longmaxi shale highstand system tract (HST) and transgressive system tract (TST) geological model were built respectively based on the rock mechanical test and acoustic emission experiment which the samples are from field outcrop and the Yuye-1 well. The Longmaxi shale two-dimension tectonic stress field during the Cenozoic was simulated by the finite element method, and the distribution of fractures was predicted. The research results show that the tectonic stress field and the distribution of fractures were controlled by lithology and structure. As a result of Cretaceous movement, there are trough-like folds (wide spaced synclines), battlement-like folds (similar spaces between synclines and anticlines) and ejective folds (wide spaced anticlines), which are regularly distributed from southeast to northwest in the study area. Since the strain rate and other physical factors such as the viscosity are not taken into account, and the stress intensity is the main factor that determines the tectonic strength. Therefore, the stronger tectonic strength leads the higher stress intensity in the eastern and southeastern study area than in the northwest. The fracture zones are mainly concentrated in the fold axis, transition locations of faults and folds, the regions where are adjacent to faults. The fragile mineral contents (such as siliceous rock, carbonate rock and feldspar) in the shelf facies shale from south of the study area are higher than in the bathyal facies and abyssal facies shale from center of the study area. The shales characterized by low Poisson’s ratio and high elastic modulus from south of the study area are easily broken during Cenozoic orogenic movement.

The Practice and Cognition of Hydraulic Fracturing Technique for Shale Gas Reservoir in Southeast Chongqing

Shale gas is an important unconventional energy resource. However its only achieved successful commercial exploitation in the United States and Canada. Shale gas well QY1 was carried out in southeast Chongqing.Taking this well as a case, the fracturing design optimization workflow and its practice are described in this paper. The fracturing feasibility of well QY1 was firstly determined by referencing all the physical parameters of target formation. Then the reservoir stress model was revised and reservoir stress profile was established as well. The reservoir simulation software (Eclipse) was applied to build reservoir geological model for predicting the gas production and determine the optimized permeability enhanced area (PEA). The unconventional fracturing model (UFM) was used to optimize the fluid volume and fracturing scale. And the final fracturing plan was made based on the optimized conclusions. This optimization workflow and the good result provide reliable technique support for the development of the shale gas reservoir in this area. Key Words: Shale gas, PEA, Fracture propagation model, UFM, Production predicting model, Optimization

A census and status review of the Endangered François' langur Trachypithecus francoisi in Chongqing, China

AbstractFrom September 2009 to September 2010 we undertook a survey of the Endangered François’ langur Trachypithecus francoisi in south-east Chongqing to compare the species' present status with historical records from the 1990s. Based on a literature review, interviews with local people and our survey we found François’ langurs in only three isolated sites, across four counties, with a total area of occurrence of c. 57 km2. The total population was estimated to be c. 200 individuals in 27 mixed sex groups. There were 21 groups (149 individuals) within a reserve (Jinfoshan), and four groups (36) in Furongjiang and two groups (13) in Heishangu were not within any reserve. The primary threat to the langur is habitat loss caused by traditional firewood use and agricultural encroachment but there is also increasing loss of forest to hydroelectric projects and construction of tourism infrastructure and facilities such as highways, hotels and telephone lines. The three sites in southern Chongqing province are adjacent to four areas in north-east Guizhou province that contain c. 60% of the wild population of the species in China. The seven sites combined are the main stronghold of this species and the geographical proximity of the sites raises the possibility of setting up ecological corridors between some of them.

Analysis of Time-Spatial Characteristics of Summer Precipition in Chongqing Region during 45 a

Using 1966~2010 year Jun.~Aug. precipitation data over 34 stations of Chongqing region, the temporal and spatial variability features were studied by applying the methods of EOF, REOF, Morlet wavelet analysis. The results indicate that the summer precipitation spatial differences are great. The summer precipitation distribution exhibits the common features as well as the spatial differences, which can be classified into four types as Northeast, Northwest, Southeast and Southwest Chongqing. The inter-annual variation characteristic in the four types is not correspondent. Northeast and Southwest ones are like a parabolic curve which have a maximum value and Southwest and Northwest ones exist upward tendency. The periods of the four types are not unanimous.

The Pb-Zn Deposits and Mineralization during Cambrian in Chongqing Area of Yangtze Platform, China

This paper presented the Pb-Zn deposits characteristics in southeast Chongqing. The Pb-Zn deposits occurred in Lower-Middle strata with develop the dolomites, limestones as ore-bearing host-rocks. They are veined, stratifed, stratoid, and lenticular in shape and locally pinch and swell with dominant ore minerals of sphalerite, galena, and pyrite . the Pb-Zn ore deposits grade changed from 0.32% to 7.06% for Pb and 4.21% to 14.29% for Zn. The Gaodongzi orebody has highest concentrations of Pb with 7.06% record and Zn with 14.29% record. The tectonic setting, ore-host rocks, wall-rock alternation, and mineral composition will control the Pb-Zn deposits distribution in Chongqing area.

The Pb-Zn Deposits and Mineralization during Cambrian in Chongqing Area of Yangtze Platform, China

This paper presented the Pb-Zn deposits characteristics in southeast Chongqing. The Pb-Zn deposits occurred in Lower-Middle strata with develop the dolomites, limestones as ore-bearing host-rocks. They are veined, stratifed, stratoid, and lenticular in shape and locally pinch and swell with dominant ore minerals of sphalerite, galena, and pyrite . the Pb-Zn ore deposits grade changed from 0.32% to 7.06% for Pb and 4.21% to 14.29% for Zn. The Gaodongzi orebody has highest concentrations of Pb with 7.06% record and Zn with 14.29% record. The tectonic setting, ore-host rocks, wall-rock alternation, and mineral composition will control the Pb-Zn deposits distribution in Chongqing area.