Stress sensitive experiments for abnormal overpressure carbonate reservoirs: A case from the Kenkiyak fractured-porous oil field in the littoral Caspian Basin

Zhao, Lun; Chen, Yefei; Ning, Zhengfu; Wu, Xia; Liu, Lifang; Chen, Xi

doi:10.1016/s1876-3804(13)60024-5

Cited by 32 publications

(23 citation statements)

References 8 publications

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“…The basic properties of the core samples used in this experiment are shown in Table 1. Various methods were proposed to study the stress sensitivity of reservoirs; among them, the confining pressure lifting method is one of the simplest and most practical test methods [32]. The According to the results obtained by core observation, casting slices, and electron microscope scanning, the main reservoir space of the Wen 23 fields is composed of secondary intergranular corrosion pore.…”

Section: Multi-cycle Formation Damage Evaluation By Flow Testmentioning

confidence: 99%

Research on Injection-Production Capability and Seepage Characteristics of Multi-Cycle Operation of Underground Gas Storage in Gas Field—Case Study of the Wen 23 Gas Storage

et al. 2020

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With the increasing energy demands of current modern society, underground gas storage (UGS) in gas fields is the most popular type of UGS used to meet the seasonal variation of gas consumption. However, compared with gas fields, UGS in gas fields has the characteristics of periodic high-speed injection and production of exploitation modes and operation rules, which causes the rules of gas-water seepage and utilization of reserves to be more particular and complicated. In this paper, based on Wen 23 gas storage, the rules of multicycle injection and production flow and the utilization of UGS pore volume were investigated. The experimental results showed that variation in porosity and permeability caused by injection and production pressure changes in Wen 23 gas storage can be neglected. The pore volume of gas storage and the degree of gas recovery increased gradually in the pre-UGS gas zone, which was higher than that of reservoirs. In the initial stage of UGS operation, the pore volume of gas storage and the degree of gas recovery were low in the gas-drive-water gas zone as a result of water invasion during the process of reservoir exploitation. During operation of multicycle high-speed injection and production, the seepage conditions in the gas-drive-water gas zone gradually improved. The higher the reservoir permeability, the greater increases in pore volume and degree of gas recovery. In the gas-water transition zone, gas and water were reciprocated and displaced with the multicycle injection-production of UGS, resulting in the gradual deterioration of pore volume and gas recovery, which remained stable at a low value. The negative effects of reservoir heterogeneity on the effective utilization of UGS occurred in the gas-water transition zone. These findings may contribute to a better understanding of the rules of multicycle injection and production flow and utilization of UGS to optimize the injection-production efficiency of Wen 23 gas storage.

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Section: Multi-cycle Formation Damage Evaluation By Flow Testmentioning

confidence: 99%

Research on Injection-Production Capability and Seepage Characteristics of Multi-Cycle Operation of Underground Gas Storage in Gas Field—Case Study of the Wen 23 Gas Storage

et al. 2020

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“…Given the multiscale nature of pore spaces, it is difficult to characterize the features of every pore type at each scale in carbonate reservoirs systematically (Yao et al, 2013;Yao et al, 2015). Meanwhile, as most of carbonate reservoirs are overpressure or abnormal overpressure, the influence of stress on these complex and various pore structures is typically significant, especially during depletion development of these reservoirs (Zhao et al, 2013;K. Zhang, Ma, et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Yang et al (2017) measured the fracture aperture of carbonate during the loading and unloading processes based on digital rocks obtained by X-ray computed tomography. The pore structure variation with respect to the stress thus resulted in the approximate exponential reductions of porosity and permeability (Zhao et al, 2013). Ameen et al (2009) generated correlation formula of porosity with mechanical properties of carbonates.…”

Section: Introductionmentioning

confidence: 99%

Stress Sensitivity of Fractured and Vuggy Carbonate: An X‐Ray Computed Tomography Analysis

et al. 2020

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Fractures, vugs, and pores constitute the main pore space in carbonate reservoirs. The associated pore structure—which is of key importance in terms of hydrocarbon production and fluid flow—varies with effective stress. However, there is a serious lack of data with regard to how precisely the pore morphology changes as a function of effective stress; we thus carried out in situ loading‐unloading experiments (up to 20 MPa effective stress) where two carbonate samples (fractured and vuggy) were examined with X‐ray computed tomography at high resolution in 3‐D. The results showed that after loading, porosity decreased exponentially, followed by an increase during unloading where it did not recover to its initial value. This was mainly because of the stress effect on large pore space (i.e., fractures and vugs). For fractured carbonate, the unrecovered porosity can be linked to similar reduction of the surface area and the average aperture of the fracture. Clearly, the changes in pore morphology were more significant in the fractured carbonate (including extension, connection, and disconnection of fractures) during both loading and unloading, while the vuggy carbonate experienced irreversible structural damage. The vuggy carbonate has bigger porosity variation than fractured carbonate to the mechanical loading‐unloading cycle. This work thus demonstrates how carbonate pore morphology changes with depth (higher effective stresses are encountered deeper in the reservoir) or during production (with hydrocarbon depletion the effective stress increases).

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“…Otherwise, it may lead to huge deviation of calculated bottom-hole pressure or production rate in comparison with the real production data. Moreover, the studies on stress sensitivity in naturally fractured vuggy carbonate gas reservoir indicate that there are strong stress sensitive effects which severely affects the production performance (Seabra et al., 2017; Wang et al., 2016a; 2016b; Zhao et al., 2013). Therefore, in this paper, we propose a semi-analytical model that considers the differences of porous characteristics and stress sensitivity for each layer in a multilayer commingled reservoir, in which some layers are naturally fractured vuggy formations represented by triple porous medium, and the others are tight formations characterized by single porous medium.…”

Section: Introductionmentioning

confidence: 99%

Production behavior evaluation on multilayer commingled stress-sensitive carbonate gas reservoir

Guo

Meng

Jia

et al. 2020

Energy Exploration & Exploitation

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Influenced by the complex sedimentary environment, a well always penetrates multiple layers with different properties, which leads to the difficulty of analyzing the production behavior for each layer. Therefore, in this paper, a semi-analytical model to evaluate the production performance of each layer in a stress-sensitive multilayer carbonated gas reservoir is proposed. The flow of fluids in layers composed of matrix, fractures, and vugs can be described by triple-porosity/single permeability model, and the other layers could be characterized by single porosity media. The stress-sensitive exponents for different layers are determined by laboratory experiments and curve fitting, which are considered in pseudo-pressure and pseudo-time factor. Laplace transformation, Duhamel convolution, Stehfest inversion algorithm are used to solve the proposed model. Through the comparison with the classical solution, and the matching with real bottom-hole pressure data, the accuracy of the presented model is verified. A synthetic case which has two layers, where the first one is tight and the second one is full of fractures and vugs, is utilized to study the effects of stress-sensitive exponents, skin factors, formation radius and permeability for these two layers on production performance. The results demonstrate that the initial well production is mainly derived from high permeable layer, which causes that with the rise of formation permeability and radius, and the decrease of stress-sensitive exponents and skin factors, in the early stage, the bottom-hole pressure and the second layer production rate will increase. While the first layer contributes a lot to the total production in the later period, the well bottom-hole pressure is more influenced by the variation of formation and well condition parameters at the later stage. Compared with the second layer, the scales of formation permeability and skin factor for first layer have significant impacts on production behaviors.

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Stress sensitive experiments for abnormal overpressure carbonate reservoirs: A case from the Kenkiyak fractured-porous oil field in the littoral Caspian Basin

Cited by 32 publications

References 8 publications

Research on Injection-Production Capability and Seepage Characteristics of Multi-Cycle Operation of Underground Gas Storage in Gas Field—Case Study of the Wen 23 Gas Storage

Research on Injection-Production Capability and Seepage Characteristics of Multi-Cycle Operation of Underground Gas Storage in Gas Field—Case Study of the Wen 23 Gas Storage

Stress Sensitivity of Fractured and Vuggy Carbonate: An X‐Ray Computed Tomography Analysis

Production behavior evaluation on multilayer commingled stress-sensitive carbonate gas reservoir

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