Characterization of the reservoir-caprock of the large basement reservoir in the Dongping field, Qaidam Basin, China

Ma, Feng; Yang, Wei; Zhang, Yongshu; Li, Hongzhe; Xie, Mei; Sun, Xiangyu; Wang, Pu; Bai, Yubin

doi:10.1177/0144598718772317

Cited by 11 publications

(17 citation statements)

References 27 publications

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“…The fluid recovery test results achieved from the drilling stem tests (DST) shown limited amount of oil flow throughout the wells. As a result, high reading of the resistivity logs in the virgin zone are corresponded to the anhydrite rock type intervals [37]. Furthermore, resistivity fluctuations were recorded by the MSFL from the flushed zone of the same intervals.…”

Section: Figurementioning

confidence: 89%

Reservoir Productivity Analysis of Intercalated limestone and Anhydrite Beds in Zagros Folded Belt, Kurdistan Region of Iraq

Rashid¹

2020

KJAR

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The Early Jurassic rock of Alan Formation in Barda Rash field has been examined using petrophysical wireline log analysis, drilling stem test, mud logging reports, drilling cutting and core samples for evaluation of reservoir potentiality and fluid production throughout heterogeneous rocks intervals in three exploration and appraisal wells. The Alan Formation consists of intercalation of light, chalky and argillaceous limestone beds with shale layers in the upper part and dominantly anhydrite layers from the middle to the lower parts of the formation. Qualitatively, weak oil shows of light brown to dark brown and blackish heavy oil have been observed while drilling. Furthermore, light brown trace oil has been recorded in the fracture surfaces of the core samples. The wireline log analysis provided an overestimated result for the hydrocarbon bearing interval identification and fluid movability index as the anhydrite layers confused the fluid distribution detection in the drilled interval. However, the combined results achieved from the mud logging reports and drilling stem tests were operated within the drilled intervals shown a limited productivity levels from the limestone beds of the Early Jurassic Alan Formation. The oil production from the studied interval does not exceed 10% and the entire production rates were composed of formation water with a trace amount of gases. As a result, the Early Jurassic Alan Formation can be considered as a tight carbonate reservoir rocks in the Barda Rash field.

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Section: Figurementioning

confidence: 89%

Reservoir Productivity Analysis of Intercalated limestone and Anhydrite Beds in Zagros Folded Belt, Kurdistan Region of Iraq

Rashid¹

2020

KJAR

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“…However, the huge thick mudstone deposited in the Jurassic strata are mainly Type II 2 -III with high content of organic matter of 1.5-3.5% and the vitrinite reflectance is more than 2.0% 12,13 , from where the generated gas was mainly transported by the deep fractures connecting the Jurassic source rock with the basement rocks in front of the Altun Mountains. Meanwhile, the Lulehe Formation in front of the Altun Mountains contains abundant anhydrite that was deposited as cement and filled the fractures and pores, leading to decreased porosity and to the formation of a tight caprock for hydrocarbon accumulation in the three wellblocks 15 . However, the anhydrite-bearing caprock is only fine local caprock that becomes thinner from the lowland to the uplift and provides super sealing conditions for the gas reservoir in Wellblock Dp1 and Wellblock Dp17, whereas it is missing in Wellblock Dp3 15 .…”

Section: Geological Settingmentioning

confidence: 99%

“…Meanwhile, the Lulehe Formation in front of the Altun Mountains contains abundant anhydrite that was deposited as cement and filled the fractures and pores, leading to decreased porosity and to the formation of a tight caprock for hydrocarbon accumulation in the three wellblocks 15 . However, the anhydrite-bearing caprock is only fine local caprock that becomes thinner from the lowland to the uplift and provides super sealing conditions for the gas reservoir in Wellblock Dp1 and Wellblock Dp17, whereas it is missing in Wellblock Dp3 15 . Jurassic gas source and anhydrite-bearing caprock are advantageous conditions for the formation of the Dongping field,but the difference of gas yield is decided by basement rock reservoir.…”

Section: Geological Settingmentioning

confidence: 99%

“…Therefore, when the field is placed on production, rapid production declines may be experienced since the reservoirs only have fracture porosity and minimal matrix porosity. Fracture reservoirs with much heterogeneity is typical in basement rocks 15,16 . The main purpose of this study is to investigate the characteristics of the basement rock reservoir and the effect of gas reserve tests, in addition to the distribution of favorable prospecting layers for the future exploration in the Qaidam Basin.…”

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confidence: 99%

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Characterization of the weathered basement rocks in the Dongping field from the Qaidam Basin, Western China: significance as gas reservoirs

Yang

Wang

et al. 2020

Sci Rep

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Reservoir quality is a critical risk factor in basement reservoirs. Researches into basement reservoirs by petrographic analysis combined with X-ray diffraction, log identification, electron microscopy, field emission scanning electron microscopy, porosity and pulse-decay permeability and core analysis have provided insights into the characterization of the commonality, diversity and difference of the weathered basement rocks as gas reservoirs in the Dongping field. Geological structures, lithology and near-surface processes control the reservoir physical property together. From Wellblock Dp 3 to Wellblock Dp 17, the high uplift gradually transforms into the low slope area towards the center of basin, with the lithology changing as well, which results in different degrees of fracture development in the bedrock in different wellblocks. The basement lithologies are granite, granitic gneiss, and limestone with slate in Wellblock Dp3, Dp1 and Dp17, respectively. Though they all provide effective reservoir space for gas accumulation, the productivity of nature gas shows significant differences. Fractures are the main store space in the three wellblocks. The development of fractures gives rise to secondary porosity around them because of physical weathering and chemical dissolution, but they generate many inhomogeneous fractures and secondary solution pores, whether on the planar distribution or in vertical. In Wellblock Dp3, high angle fractures were generated under the action of structural stress mechanism, with a large number of secondary pores. The porosity is between 0.1 and 23.2%. In Wellblock Dp 1, low angle fractures were the main storage space, with plenty of solution pores mainly in melanocratic minerals. The porosity is between 0.1 and 18.8%. In Wellblock Dp 17, where short and dense fractures developed, the porosity is between 0.1 and 10.3%. The data indicate that the granite in the uplift in Wellblock Dp3 has better reservoir properties due to the stronger physical weathering and chemical dissolution. As the porosity gradually decreases towards the slope and low-lying area, the more favorable exploration area should be the uplift and slope area in the depression area. However, the effective caprock developed locally in Wellblock Dp3, which affected the gas accumulation. Meanwhile, the reservoirs’ petrophysical properties showed distintive variation with different depths in different wellblocks. High productivity layers are under the 200 m, 100 m and 200 m depths from the top of the basement rocks in Wellblock Dp 3, Wellblock Dp 1 and Wellblock Dp 17, respectively. This suggestion in this study will be of significance for guiding oil and gas exploration in front of the Altun Mountains.

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“…With the intensification of the use of unconventional energy resources, the successful exploration and development of shale gas in North America has caused an upsurge in global shale gas development (Bahadur et al, 2015;Chalmers et al, 2012;Chen et al, 2018;Clarkson et al, 2013;Dong et al, 2017;Lei et al, 2019;Ma et al, 2018b;Maitlo et al, 2019). It is estimated that there is 22016 Tcf of shale gas available worldwide, which is almost equal to the combined amount of coal-bed methane and tight sandstone gas (Ma et al, 2018a;Lyu et al, 2015;Yue et al, 2019). During oil and gas well drilling, wellbore stability must be maintained.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of the pomelo peel powder as novel shale inhibitor in water-based drilling fluids

Zhang

Sun

et al. 2019

Energy Exploration & Exploitation

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The hydration and swelling of shale is a persistent challenge in the drilling of oil and gas wells. Many methods of reducing shale hydration and swelling have been developed; however, most of them are high-cost or release pollutants. In this study, we explored the use of pomelo peel powder as a novel additive to water-based drilling fluids for inhibiting shale hydration swelling in an environmentally sustainable manner. We compared the performance of the drilling fluid containing pomelo peel powder to that of traditional shale inhibitors, such as potassium chloride and polyamine. Moreover, hydration inhibition, bentonite precipitation dynamic linear expansion, rolling recovery, and adsorption experiments were conducted to investigate the inhibitory effects of the pomelo peel powder on shale. The results show that the pomelo peel powder solution with a mass fraction of 1% and an optimised particle size of over 160 mesh was acidic, could prevent shale collapse, and could reduce mud loss by filtration. The rolling recovery of shale cuttings reached 95% with the addition of pomelo peel powder, and the powder could also inhibit the hydration of bentonite, prevent clay minerals from dispersing in a solution, and reduce the expansion of bentonite. The inhibitory effect of the powder was slightly worse than that of potassium chloride and polyamine; however, the difference was not significant. The anti-swelling mechanism of pomelo peel powder was then analysed, and we found that fresh pomelo peel powder contains a high number of active substances that reduce the filtration of mud, improve its rheological properties, and hinder the hydration and expansion of clay. Pomelo peel is available worldwide and is easy to obtain as a shale inhibitor. Thus, using pomelo peel powder can effectively alleviate ecological pressure and reduce environmental pollution.

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Characterization of the reservoir-caprock of the large basement reservoir in the Dongping field, Qaidam Basin, China

Cited by 11 publications

References 27 publications

Reservoir Productivity Analysis of Intercalated limestone and Anhydrite Beds in Zagros Folded Belt, Kurdistan Region of Iraq

Reservoir Productivity Analysis of Intercalated limestone and Anhydrite Beds in Zagros Folded Belt, Kurdistan Region of Iraq

Characterization of the weathered basement rocks in the Dongping field from the Qaidam Basin, Western China: significance as gas reservoirs

Experimental study of the pomelo peel powder as novel shale inhibitor in water-based drilling fluids

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