The influence of fracture cements in tight Paleogene saline lacustrine carbonate reservoirs, western Qaidam Basin, northwest China

Zeng, Lianbo; Tang, Xiaomei; Wang, Tiecheng; Gong, Lei

doi:10.1306/04181211090

Cited by 47 publications

(13 citation statements)

References 18 publications

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“…Specifically, production capacity was high at the initial stage with an average well yield of 371 bbls/day but declined fast at the later stage, e.g., it decreased to a low value with high water injection pressure after water injection. Continuous pressure boosting increased the water cut greatly, exhibiting the typical production behavior of fractured reservoirs (Zeng et al, 2012;Gong et al, 2019a). The current recovery rate and average well yield are only 8.1% and 13.3 bbls/day, respectively, whereas the water cut is up to 91.6%.…”

Section: Introductionmentioning

confidence: 93%

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Wang

Muhtar

et al. 2021

Front. Earth Sci.

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Natural fractures play an important role in the seepage system of Paleogene sandstone reservoirs at Nanpu Sag. Characteristics and formation mechanisms of natural fractures and stress-sensitivity permeability are comprehensively investigated and their impact on water injection is discussed based on core and log data (FMI and diplog data) as well as stress-sensitivity permeability measurement. Results show that high-angle shear fractures, including NE-SW strike fractures and NW-SE strike fractures, are widely developed in the study area, which were primarily developed during the late Paleogene and late Neogene. The present maximum horizontal principal stress is orientated at N60°–80°E, approximately parallel to the NE-SW fractures, contributing greatly to the seepage system at the early oilfield development stage. Fractures in the study area can be divided into three phases and are characterized by obvious stress-sensitivity permeability, which is closely related to fracture aperture and throat size. Since the fracture occurrence enhances stress sensitivity of permeability, it is necessary to regulate well pattern based on dynamic behaviors of fractured reservoirs at different development stages.

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Section: Introductionmentioning

confidence: 93%

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Wang

Muhtar

et al. 2021

Front. Earth Sci.

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“…In addition, the platform-margin shoals were in a high-energy environment, sediments were cleanly sorted, the grain content was high, and the shale content was low (Ehrenberg 2006;Fabrizio 2012;Faith et al 2012;Ikram et al 2009;Jones et al 1992;Li et al 2011a, b;Paul 2010;Pomar 2001;Read 1985;Tan et al 2008;Tekin et al 2010;Tucker 1985;Vazirri-Moghadam et al 2006;Zeng et al 2012). Therefore, after early compaction the platform-margin shoals easily formed solid grain-supported frameworks.…”

Section: Sedimentary Environmentmentioning

confidence: 99%

“…important in carbonate reservoirs, and diagenesis strongly affects reservoirs (Amadi et al 2012; Berra 2012; Cathy 2011; Ehrenberg et al 2005; Esrafili-Dizaji and Rahimpour-Bonab 2009;Gareth et al 2006;Hollis 2011; Paola et al 2010;Rick et al 2006;Zeng et al 2012).…”

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confidence: 99%

Differences between the platform-margin shoal reservoirs and the platform-interior shoal reservoirs of the Middle Triassic Leikoupo Formation, Sichuan Basin, China

Ding

Tan

Ling

et al. 2014

Carbonates Evaporites

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The carbonate shoal grainstone reservoirs of the Middle Triassic Leikoupo Formation in the Sichuan Basin provide a typical example of gas exploration in shoal carbonate reservoirs. The carbonate shoal reservoirs in Leikoupo Formation are of two types: platformmargin shoals and platform-interior shoals. Based on a comprehensive data analysis, and through analysis and correlation of grain shoal reservoir characteristics, it has been shown that there are significant differences between platform-margin and platform-interior shoal reservoirs in terms of the types of reservoir space, the relationship between porosity and permeability, and the pore throat structures. The pores in the platform-margin shoal reservoirs are mainly relict intergranular pores and intergranular dissolution pores, and their porosity and permeability show a good positive correlation. The throats are thick and the pore throats have a good distribution. Isolated intragranular solution pores and moldic pores are mainly developed in the platform-interior shoal reservoirs. There is a weak positive correlation between porosity and permeability, pore throats are less developed, and the pore throats have poor configurations. Differences in sedimentary environment and diagenetic evolution are the primary causes of the different reservoir characteristics of the two shoal facies. The water body in the platform-margin shoal deposits had a higher energy than that in the platform-interior shoal deposits, and its wave base was deeper that of the platform-interior shoals. The shoal bodies at the platform margin are much thicker than those in the platform interior. The grainstones of platform-margin shoals are much better sorted. The rocks have undergone compaction during most post-depositional stages. The thicker grainstones of the platform-marginal shoals preserved their original intergranular pores better than the lowerthickness grainstones in the platform-interior shoals. This was favorable for formation of intergranular dissolution pores during later burial. In contrast, the grainstones of the platform-interior shoals are less thick and early intergranular cements are well developed, resulting in large-scale loss of the original intergranular pores. However, as a result of selective dissolution by early fresh water in the meteoric diagenetic environment, intragranular solution pores and moldic pores were readily formed. Thus, the platform-margin shoal reservoirs show preservation of the original intergranular pores enhanced by burial dissolution, but the platforminterior shoal reservoirs are mainly the result of early selective dissolution by meteoric fresh water.

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“…Lacustrine carbonate rocks are widely distributed across the world (Zeng et al, 2012;Bohacs et al, 2013;Gareth and Xiao, 2013;Muniz and Bosence, 2018;Cao et al, 2019), and are common oil and gas reservoirs (Peng, 2011;Tang et al, 2015;Bao et al, 2015;Song et al, 2017;Cao et al, 2017Wang et al, 2019. Coquina is an unique lacustrine carbonate rock, mainly composed of shells, can also be profitable reservoir rock.…”

Section: Introductionmentioning

confidence: 99%

Evaluation Methods of Profitable Tight Oil Reservoir of Lacustrine Coquina: A Case Study of Da'anzhai Member of Jurassic in the Sichuan Basin

Pang

Tao

Zhang

et al. 2020

Acta Geologica Sinica (Eng)

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Based on core observation, cast and fluorescent thin sections, FESEM and ESEM, coquina in Da'anzhai Member of Jurassic in Sichuan Basin were examined systematically. Together with production data and logging evaluation, a method for lacustrine coquina evaluation based on geological theory was established up. In the article, two aspects of the study were elaborated, characteristics of favorable reservoirs, and a "five-step" evaluation method for favorable coquina reservoir. According to the correlation between porosity and production data, porosity is not effective in finding high quality coquina reservoir of this area. Whereas micro research of reservoir samples from a high productivity well revealed that sparry coquina is the best lithofacies, with the most developed micro storage space of various kinds. After the favorable reservoir was sorted out, a five-step method evaluating the coquina reservoir was worked out. Correlation of GR value and rock types suggests that GR<30 API is an effective evaluation parameter in identifying profitable reservoir lithofacies. Meanwhile, the combination of profitable reservoir rock thickness and production data revealed that the reservoirs with the highest potentiality are those with thickness of 3-18 m. Fractures are more developed in faults, folds and structural noses in the study area. Organic acid is discharged massively before the peak of hydrocarbon generation, leading to the formation of dissolution pores in the reservoir. The evaluation of organic acid was made by using the source rock indexes. After evaluating the four factors, and compiling their distribution maps, the maps were overlapped to predict favorable reservoir zones, and 7 first class and 9 second class favorable zones of coquina were picked out.

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The influence of fracture cements in tight Paleogene saline lacustrine carbonate reservoirs, western Qaidam Basin, northwest China

Cited by 47 publications

References 18 publications

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Differences between the platform-margin shoal reservoirs and the platform-interior shoal reservoirs of the Middle Triassic Leikoupo Formation, Sichuan Basin, China

Evaluation Methods of Profitable Tight Oil Reservoir of Lacustrine Coquina: A Case Study of Da'anzhai Member of Jurassic in the Sichuan Basin

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