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Jia H.,China University of Petroleum - Beijing | Ji H.,China University of Petroleum - Beijing | Wang L.,Petrochina | Gao Y.,Petrochina | And 2 more authors.
Journal of Petroleum Science and Engineering | Year: 2017

The conglomeratic reservoir in the Mahu depression, northwestern margin of the Junggar basin, Northwestern China has become an important exploration target. In this study, we use well and core data to investigate the characteristics and controlling factors of conglomeratic fan-delta reservoirs. The reservoir studied here developed in a retreating fan-delta complex that is dominated by conglomerate lithofacies and conglomeratic sandstone lithofacies. A petrological analysis shows that the reservoir exhibits poor compositional maturity and textural maturity. A physical property analysis shows that the reservoir exhibits extremely low porosity and extremely low permeability, as well as strong heterogeneity in the vertical and planar views. The depositional environment and compaction result in extremely low porosity and extremely low permeability in the reservoir. About 66% porosity was destroyed by the compaction. Fan-delta evolution and provenance control the macroscopic variations in reservoir quality. Muddy matrix content, grain size and dissolution control the microscopic variations in reservoir quality. About 52.5% porosity was induced by the dissolution. This reservoir study can be compared to fan-deltas that developed in marine-connected rift basins during early stages of extension and to nearshore subaqueous fans in East China. Additionally, the results of this study may provide a reference for such systems and provide a subsurface case for similar fan-delta outcrop studies and facies reservoir modelling. © 2017 Elsevier B.V.

Yin Z.F.,shanxi Yanchang Petroleum Group Company | Bai Z.Q.,China National Petroleum Corporation | Zhou W.J.,Tarim Oilfield Company | Li B.,China National Petroleum Corporation
Surface and Interface Analysis | Year: 2010

Potentiodynamic sweep and electrochemical impedance spectroscopy measurements were applied to investigate the effects of both temperature and acetic acid (HAc) on the anodic and cathodic reactions in CO2 corrosion of P110 steel in 3.5% NaCl solution. The temperatures were controlled at 30 and 60 °C. The concentrations of HAc were controlled at 0,1000,3000 and 5000 ppm. In this work, the corrosion parameters of polarization curves, such as corrosion potential (Ecorr), corrosion current density (icorr), and anodic and cathodic branch slopes (ba and bc), are presented and discussed in detail. In addition, the equivalent circuit models and ZsimpWin software were utilized to discuss the Nyquist plots. The plots showed that the Ecorr values shifted in the positive direction as the HAc concentration increased. The icorr values increased with the increase in HAc concentration, indicating that HAc could accelerate the corrosion. The impedance spectra measured at 30 and 60 °C have different time constants and characterization. The coverage fraction θ and the thickness L of corrosion film are two most important controlled variables that influence and control the CO2 corrosion mechanisms. Copyright © 2010 John Wiley & Sons, Ltd.

Zhang F.-Q.,Xi'an Shiyou University | Zhang F.-Q.,Northwest University, China | Wang Z.-L.,Northwest University, China | Wu F.-L.,Xi'an Shiyou University | And 3 more authors.
Zhongguo Shiyou Daxue Xuebao (Ziran Kexue Ban)/Journal of China University of Petroleum (Edition of Natural Science) | Year: 2012

By restoring the overpressure of main accumulation period in the deep of Kelasu structural belt of Kuqa depression and Yanchang formation of Yishan slope of Ordos Basin, the possible dynamic conditions during the process of hydrocarbon migration in the low permeability-tight sandstone reservoir were estimated combined with the analysis on reservoir physical properties evolution. The results show that the main dynamics of hydrocarbon migration in the low permeability-tight sandstone reservoir is characterized by diversity. The reservoir becomes tight in the natural gas accumulation period in the deep of Kelasu structural belt. The main dynamic of natural gas migration is the overpressure formed by the multiple factors of high-rate deposition, hydrocarbon generation, and tectonic compression and so on. The reservoir does not become tight in the oil infill injection early and middle stage in Yanchang formation of Yishan slope of Ordos Basin. The oil migrates laterally due to buoyancy. The reservoir becomes tight in the oil infill injection late stage. It mainly migrates laterally along the residual pathways that are oil-wet due to long-term contact with oil. The main dynamic of oil migration is capillary force and the difference of excess pressure among the reservoirs also plays a role in the oil migration. So the oil migration of main accumulation periods in Yanchang formation of Yishan slope of Ordos Basin is the joint action of the multi-stage and multi-dynamic.

Yang C.,China University of Geosciences | Yang C.,Key Laboratory of Shale Gas Exploration and Evaluation | Zhang J.,China University of Geosciences | Zhang J.,Key Laboratory of Shale Gas Exploration and Evaluation | And 8 more authors.
Journal of Natural Gas Science and Engineering | Year: 2016

The purpose of this article is to quantitatively reveal the compositional controls on pore-size distribution (PSD) within the transitional Lower Permian Shanxi Shales. Our results demonstrate that the average pore-size (APS) of Shanxi Shales is approximately 12–24 nm and that the size is essentially controlled by clay minerals. The ‘closed area’ of the hysteresis loop, the most prevalent feature in microporous materials, can qualitatively reflect the PSD. A rule regarding the PSD is confirmed that the larger the closed area is, the smaller the pores are, and vice versa. Type III kerogen in the Shanxi Shales is shown to be composed of nearly nonporous organics, whereas the clay minerals possess large amounts of inter-layer pores; therefore, the PSD of the Shanxi Shales is determined by the clay-hosted pores, whose pore-size intervals differ by clay mineral type. Specifically, I/S-hosted pores possess both intra-aggregate pores with a characteristic 3–4 nm pore size and inter-aggregate pores with a characteristic 50–60 nm pore size; of these, the former predominates. On the other hand, the pores associated with the other clay mineral types (including kaolinite, illite, and chlorite) are mostly inter-aggregate pores with a characteristic 50–60 nm pore size. Overall, our research contributes to understanding the physical properties of the transitional Shanxi Shales and revealing their nano-scaled pore-size distribution and variation. © 2016 Elsevier B.V.

Guo X.,Southwest Petroleum University | Meng X.,Southwest Petroleum University | Meng X.,Shanxi Yanchang Petroleum Group Corporation Ltd. | Du Z.,Southwest Petroleum University | And 3 more authors.
Oil Gas European Magazine | Year: 2015

TSS-12-3 [Trimer sulfonate surfactant 1, 2, 3-tri(2-oxoypropylsulfonate-3-alkylether-pr opoxyjpropane] is a kind of anionic Gemini surfactant with three sulfonate groups and three dodecyls. It has higher surface activities thus lower CMC, lower γemer, lower IFT and better foaming properties than single chain surfactants, so it is used as a foaming agent in foam flooding to displace oil in harsh reservoirs. Systematic experiments of foam flooding after water flooding have been performed for high salinity reservoirs. The foaming ability, stability and FCI are the key factors to ensure high performance of oil recovery. The foam flooding formula is optimized by good performance of foaming ability, stability and FCI. The co-injection of foam is the most effective mode and the alternative injection of gas and solution is the poorest. The gas liquid ratio can also affect the flooding efficiencies significantly. The optimized gas liquid ratio isproposedas 4:1 for co-injection mode at the reservoirs condition. Comparison of foam flooding with gas flooding, surfactant flooding and polymer flooding indicates that EOR of foam flooding is highest. Results of dual core flooding experiments indicate that foam flooding with polymer can contribute 11-20% OOIP (original oil in place) recovery. The obvious increase of oil recovery during foam flooding indicates that nitrogen foam flooding has excellent profile control ability. Polymer enhancing foam can flow into the low permeability zone and block thief zone for high salinity reservoirs. © 2015 URBAN-VERLAG Hamburg/Wien GmbH.

Jia H.,China University of Petroleum - Beijing | Ji H.,China University of Petroleum - Beijing | Li X.,Shanxi Yanchang Petroleum Group Corporation | Zhou H.,Petrochina | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2016

In this study, we use seismic reflection, logging and core data to investigate the depositional systems and their controlling factors in the lower Triassic in the northwestern margin of Junggar basin. The succession shows strong lateral and vertical facies variation. The facies associations indicate the development of conglomeratic fan-delta system, with characteristics of fining-upward and landward migration of facies belts. A critical balance between progradation, aggradation, and retrogradation controlled the evolution of delta successions within an overall transgressive regime. Migration of the locus of active faulting exerted the primary control on fan-delta thickness. Variations on the sandy component and gravel type within the fan-delta system among different units indicate the control of provenance. The climate significantly influenced the mode of sediment transfer from the feeder system to the basin. The significant climate change from arid to humid played a primary role in controlling the fan-delta architecture. Our study suggests that in tectonic-active basin, the controls of tectonics on the sequence stratigraphy are still fundamental. However, during the tectonic quiescence or rift-depression transition stage, significant changes of climate would play a primary role in controlling the sediment dispersal. The current study reveals that the hydrocarbon reservoir shows a landward migration trend within a retreating fan-delta system. © 2016 Elsevier Ltd.

Ni J.,Research Institute of Shaanxi Yanchang Petroleum Group | Ni J.,Northwest University, China | Ren Z.,Northwest University, China | Wang X.,Shanxi Yanchang Petroleum Group Corporation Ltd. | Zhan Z.,Research Institute of Shaanxi Yanchang Petroleum Group
Energy Exploration and Exploitation | Year: 2013

It is quite difficult to apply the regular well patterns into the development of oilfields due to a series of factors like the geology complexity, the limitation of development cost and the operability in real reservoir. Therefore, a new kind of well pattern is proposed to deal with the above problem. This method focuses on developing multilayer reservoir by the stepped horizontal well, which is deployed with two vertical injectors at both sides, respectively. According to the newly established well pattern, the corresponding productivity formula for the stepped horizontal is deduced. In this process, the stepped horizontal well is divided into several sections by each layer in the first. Secondly, the productivity equation of one section among them is derived on the basis of conformal transformation and potential flow theory, the other section is dealt with in the same way. Thirdly, the simultaneous equations of productivity for each section are solved on the basis of nodal analysis. Besides, the pressure drop loss of wellbore flow in the horizontal section is also taken into consideration. Finally, the total productivity is worked out.In order to prove the applicability of the established productivity formula for the proposed well pattern, the data of well Z12-33 in Zhaozhou oilfield are adopted to calculate the total productivity, the results indicate that the error between calculated value and real production is small, which proves the reliability of this formula. Therefore, this formula can be applied into the real reservoirs to aid the oilfields development.

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