Artificial-neural-network (ANN) based proxy model for performances forecast and inverse project design of water huff-n-puff technology

Rao, Xiang; Zhao, Hui; Deng, Qiao

doi:10.1016/j.petrol.2020.107851

Cited by 31 publications

(13 citation statements)

References 13 publications

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“…With the depletion of conventional resources and the increase in energy demand, low-permeability oil reservoirs play an important role in the world energy map (Wang et al, 2018;Rao et al, 2020;Feng et al, 2021). Due to the poor physical properties of the reservoir, that is, small pore size, low porosity, and low permeability, hydraulic fracturing becomes the necessary technology to develop these types of reservoirs in a commercial and effective way (Takahashi and Kovscek, 2010;Ren et al, 2016;Huang et al, 2021a;Huang et al, 2021b).…”

Section: Introductionmentioning

confidence: 99%

“…This is because the variation of permeability has contradictory effects on spontaneous imbibition, that is, the decrease in capillary pressure and the increase of water flow space. Rao et al (2020) investigated the mechanisms of water puff-n-huff in low-permeability reservoirs with complex fracture networks, and the results showed that the surface area of fractures determines the imbibition efficiency. His results suggest that increasing the complexity of fractures can promote fluid exchange between the fractures and the matrix.…”

Section: Introductionmentioning

confidence: 99%

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Study of Water Huff-n-Puff in Low-Permeability Oil Reservoirs With Horizontal Fractures: A Case Study of Chang 6 Reservoir in Yanchang, China

Meng

Song

Zhang³

et al. 2022

Front. Earth Sci.

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Water huff-n-puff is an effective technology to enhance oil recovery (EOR) of low-permeability reservoirs, which are usually developed with hydraulic fracturing. Fluid exchange between fractures and the matrix is the main EOR mechanism. However, the presented water huff-n-puff simulations usually assume vertical fracture morphology, while the horizontal fractures formed in shallow reservoirs are rarely reported. In this study, we first introduced the water huff-n-puff process in a low-permeability oil reservoir with horizontal fractures and described the multiphase flow characteristics during the huff, soak, and puff stages. Then combined with a series of experiments, a comprehensive method is used to determine the key flow parameters, that is, capillary pressure and relative permeability. Finally, using the Chang 6 reservoir as an example, a series of numerical simulations were conducted to demonstrate the effect of water huff-n-puff on the well performance in this field. The simulation results showed that oil production is mainly affected by the injection volume and injection rate, while water production mainly depends on the well shut-in time. For a typical well in this field, the optimal injection volume, injection rate, and well shut-in time are 300 m3, 10 m3/d, and 30 days, respectively. In addition, our results showed that increasing the number of cycles not only benefits fluid exchange but also enhances the formation pressure. Both of them can accelerate the development of low-permeability oil reservoirs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Study of Water Huff-n-Puff in Low-Permeability Oil Reservoirs With Horizontal Fractures: A Case Study of Chang 6 Reservoir in Yanchang, China

Meng

Song

Zhang³

et al. 2022

Front. Earth Sci.

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“…Scholars have conducted research on WHP technology in tight oil reservoirs, including applicable conditions, oil recovery mechanisms, and influencing factors. − However, the following problems still exist. (1) There are very few physical simulation experiments for oil recovery by WHP in tight oil reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Study on Influencing Factors of Water Huff-n-Puff Oil Recovery in Matrix-Fracture Systems of the Tight Sedimentary Tuff Reservoirs

Yang

Jin

et al. 2022

ACS Omega

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Tight sedimentary tuff reservoirs (TSTRs) are a new type of tight oil reservoirs, which are mainly developed by water huff-n-puff (WHP). However, there is no quantitative study on the effect of water injection pressure (WIP) and fracture density (FD) on the oil recovery effect of WHP, and the reasons for the low flow-back rate (FR) of the injected water are also not fully explained. In this study, the real cores of TSTRs were used to simulate the seepage state of the matrix-fracture systems of the reservoir, the effects of WIP and FD on the WHP were quantitatively studied, and the reasons for the low FR of the injected water were comprehensively analyzed. The result shows that in five cycles of WHP, the recovery factor (RF) of the core only increases from 8.72 to 10.91% with the WIP increasing from 25 to 30 MPa. However, when the WIP is 40 MPa (rock breakdown pressure), the RF of the core reaches 16.47%, indicating that overfracture-pressure water injection has an obvious improvement effect on the oil recovery effect of WHP in TSTRs. Increasing the FD can also significantly improve the RF and oil recovery efficiency (ORE) of WHP in TSTRs. When the FD of the core increases from 0.34 to 0.44 cm –1 , the RF of five cycles of WHP increases by 9.26%, the ORE increases by 8.61%, and the FR of the injected water decreases by 0.56%. The reasons for the low FR of the injected water in WHP in tight oil reservoirs are matrix water locking, fracture water locking, and reservoir nonconstant-volume water locking. The study can provide an important reference for the efficient development of the WHP in TSTRs.

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“…However, the following problems also exist. − (1) Although scholars have carried out physical simulation experiments of WIHP, the experimental cores used are small-sized plunger cores. For relatively homogeneous reservoirs, this is desirable, but for non-homogeneous reservoirs, small-scale cores cannot reflect the physical properties and seepage characteristics of the reservoir, and more representative full-diameter large-sized cores must be used.…”

Section: Introductionmentioning

confidence: 99%

Influence of Water Injection Pressure and Method on Oil Recovery of Water Injection Huff and Puff in Tight Volcanic Oil Reservoirs

Yang

Dong

et al. 2022

ACS Omega

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The water injection huff and puff (WIHP) technology is regarded as one of the important means to improve the recovery factor (RF) of tight volcanic oil reservoirs (TVORs), but the influence of water injection pressure (WIP) and water injection method (WIM) on the oil recovery effect of WIHP has been rarely reported. In this paper, we first collected the real full-diameter cores from a TVOR and then simulated the distribution characteristics of fractures and matrix pores after hydraulic fracturing of the reservoir through the combination and cutting of the cores. Finally, we used the large-sized physical simulation device for tight oil WIHP that can bear high temperature and high pressure and a nuclear magnetic resonance instrument to conduct experiments of five cycles of constant pressure WIHP (CWIHP) with WIPs of 25, 32.5, and 40 MPa and step-by-step pressure rising WIHP (SWIHP) (the WIP was 25, 30, 33, 37, and 40 MPa in order) and obtained the liquid production law and mechanism of tight volcanic rock (TVR) under CWIHP and SWIHP. The result shows that under the CWIHP mode, the RF of TVR has a good power-law-positive correlation with the WIP. However, with the increase of WIHP cycles, the RF of CWIHP always decreases rapidly. In the WIHP of TVR, the injected water mainly collects oil in large pores (the pore radius is greater than 0.1 μm), and the closer the area to the outlet end of oil production and the higher the fracture density, the higher the RF. SWIHP can also effectively improve the RF of TVR, but compared with CWIHP with a WIP of 40 MPa, the amount of recovered oil decreases relatively slowly with the increase of WIHP cycles. In the first two cycles of the five cycles of WIHP, the RF of CWIHP was higher, but from the third cycle, the RF of SWIHP begins to be greater, and the more the number of cycles of WIHP, the more obvious the advantage of SWIHP. When the number of WIHP cycles exceeds 5, the oil recovery effect and the economy of SWIHP are better. This study can provide a solid theoretical basis for the efficient development of WIHP in TVORs.

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Artificial-neural-network (ANN) based proxy model for performances forecast and inverse project design of water huff-n-puff technology

Cited by 31 publications

References 13 publications

Study of Water Huff-n-Puff in Low-Permeability Oil Reservoirs With Horizontal Fractures: A Case Study of Chang 6 Reservoir in Yanchang, China

Study of Water Huff-n-Puff in Low-Permeability Oil Reservoirs With Horizontal Fractures: A Case Study of Chang 6 Reservoir in Yanchang, China

Study on Influencing Factors of Water Huff-n-Puff Oil Recovery in Matrix-Fracture Systems of the Tight Sedimentary Tuff Reservoirs

Influence of Water Injection Pressure and Method on Oil Recovery of Water Injection Huff and Puff in Tight Volcanic Oil Reservoirs

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