Rate transient analysis for coupling Darcy flow and free flow in bead-string fracture-caved carbonate reservoirs

Li, Yong; Yu, Qingyan; Jia, Chunxia; Liu, Pengcheng; Wang, Qi; Wang, Daigang

doi:10.1016/j.petrol.2020.107809

Cited by 17 publications

(5 citation statements)

References 30 publications

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“…In addition, on the basis of drilling reservoirs without encountering a vug, Du et al (2020) simplified vugs into concentric rings and developed a radial multilayer and multi-cavity composite reservoir well testing analysis model, which quantitatively characterizes the number of vugs. Li et al (2020) and Li et al (2021) proposed a theoretical well testing model of seam-hole-type carbonates with a bead structure. In summary, different models for well testing interpretation of carbonate reservoirs with large vugs were developed and applied in example production.…”

Section: Large-scale Vug Well Testing Modelsmentioning

confidence: 99%

Research progress and challenges of flow mechanisms and well testing models in carbonate reservoirs

Liang,

Chen,

Yan

2023

Front. Energy Res.

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Section: Large-scale Vug Well Testing Modelsmentioning

confidence: 99%

Research progress and challenges of flow mechanisms and well testing models in carbonate reservoirs

Liang,

Chen,

Yan

2023

Front. Energy Res.

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“…In this flow procedure, only the vertical flow is considered. According to the work of Li et al [25] and Wei et al [26], the pressure in any part of the cave will immediately turn into balanced. Therefore, the cave can be regarded as an equipotential body.…”

Section: Mathematicalmentioning

confidence: 99%

Pressure Transient Analysis for a Well Drilling into a Large-Size Cave in Fracture-Caved Carbonate Gas Reservoirs

Jin

2022

Geofluids

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This paper studies the influence of large-size cave on pressure transient characteristics in fracture-caved carbonate gas reservoirs (FCCGR). With the rapid increase of energy demand, the exploration and development of unconventional oil and gas becomes more and more important. In recent years, many FCCGR have been discovered in western China and contribute significantly to Chinese gas reserves. However, with the presence of large-size cave, FCCGR have complex pore structures and strong heterogeneity. Traditional pressure transient analysis models cannot describe the gas flow accurately. This paper develops a novel pressure transient analysis model for FCCGR by coupling the fluctuating pressure and minor energy loss. Based on the solutions, the typical curves are plotted to analyze the pressure transient characteristics. It is found that the flow process can be subdivided into six stages, including the following: (I) wellbore storage, (II) first transition stage, (III) cave storage, (IV) second transition stage, (V) interporosity flow, and (VI) radial flow. The findings indicate that a concave is added, and the wellbore storage occurs earlier due to the existence of cave. Then, the influences of key parameters are studied. The pressure propagation coefficient and cave volume factor influence the stages I, II, III, and IV. When pressure propagation coefficient increases, the wellbore storage becomes larger and cave storage becomes smaller. The first concave moves to upper right. When cave volume factor increases, the wellbore storage occurs earlier and the curves move left in stage I. Interporosity flow factor and storage ratio influence the location and depth of the second concave. Finally, a field gas well is interpreted by using the proposed model, which verifies the reliability and correctness of the model. The findings of this study can help to better understand the influence of large-size cave on pressure transient characteristics. In addition, it can help engineers invert the cave volume, which is of great significance for the development in FCCGR.

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“…1). The rock matrix has extremely low porosity and permeability due to extra-large buried depths, and hence the flow is neglected in most cases [9,10]. The large caves are usually not filled, whose size can range from meters to even tens of meters [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…Afterwards, Liu et al [35] established a well test model of multi fracture-vug horizontal combination in fractured vuggy carbonate reservoirs. Li et al [10] derived a semianalytical solution for horizontal beads-on-string fracturecaved carbonate reservoirs. The dimensionless type curves for rate transient analysis are plotted and a case study is conducted to evaluate the reservoir and well properties.…”

Section: Introductionmentioning

confidence: 99%

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Parameters evaluation of fault-karst carbonate reservoirs with vertical beads-on-string structure based on bottom-hole pressure: Case studies in Shunbei Oilfield, Tarim Basin of Northwestern China

Cao

Cheng

Chen³

et al. 2021

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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Tarim Basin newly discovered the fault-karst carbonate reservoirs, which are formed by the large-scale tectonic fault activities and multiple-stage karstification. Four kinds of mediums coexist in the reservoirs, including the large cave, vug, tectonic fracture and matrix. The tectonic fractures interconnect with large caves in series to form the vertical beads-on-string structure, which is the most common connection pattern in reservoirs. To provide a well test method for evaluating this type of structure, this work firstly presents a multi-fracture-region multi-cave-region series connection physical model by simplifying vertical beads-on-string structure. We consider four kinds of mediums in the proposed physical model, including large caves, small vugs, high-angle tectonic fracture and rock matrix. The fracture regions mainly contain fracture, vug and matrix mediums. The cave regions contain cave medium. The corresponding mathematical model is also developed, in which the flow in fracture regions obeys the Darcy’s law, while the flow in cave regions is assumed to obey free flow. Furthermore, the gravity is taken into account because the flow is along the vertical direction. Then the typical flow regimes are analyzed and sensitivity analysis is conducted on crucial parameters. Results indicate that (a) the typical feature of vertical beads-on-string structure on type curves is that the cave storage regimes and linear flow regimes alternately appear; (b) the type curves will exhibit the cave storage regimes with unit-slope pressure derivative for the existence of large caves, which is different from the inter-porosity flow regimes for the existence of the vugs (slope ≠ 1); (c) the gravity effect could lead to unit-slope pressure and pressure derivative curves, which can be regarded as closed boundary in a peculiar sense; (d) gravity effect is difficult to be observed from well test curves with about 2-weeks test duration in real application. Finally, two cases from Shunbei Oilfield are interpreted to illustrate the practicability and feasibility of proposed method.

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Rate transient analysis for coupling Darcy flow and free flow in bead-string fracture-caved carbonate reservoirs

Cited by 17 publications

References 30 publications

Research progress and challenges of flow mechanisms and well testing models in carbonate reservoirs

Research progress and challenges of flow mechanisms and well testing models in carbonate reservoirs

Pressure Transient Analysis for a Well Drilling into a Large-Size Cave in Fracture-Caved Carbonate Gas Reservoirs

Parameters evaluation of fault-karst carbonate reservoirs with vertical beads-on-string structure based on bottom-hole pressure: Case studies in Shunbei Oilfield, Tarim Basin of Northwestern China

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