A modified embedded discrete fracture model to study the water blockage effect on water huff-n-puff process of tight oil reservoirs

Rao, Xiang; Cheng, Linsong; Cao, Renyi; Jia, Peng; Wu, Yonghui; H, Liu; Zhao, Yuying; Chen, Ying

doi:10.1016/j.petrol.2019.106232

Cited by 27 publications

(6 citation statements)

References 31 publications

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“…Rao et al analyzed the influence of the water lock effect on the water huff-n-puff process of tight reservoirs by numerical simulation. 30 Wang et al 31 investigated the boundary layer effect in the process of water injection huff-n-puff. A layer of nonflowing film reduced the output and accelerated the decline of output.…”

Section: Introductionmentioning

confidence: 99%

Oil Production Mechanism of Water Injection Huff-n-Puff for Enhancing Oil Recovery in Tight Sandstone Reservoir

Ji,

Yu,

Liu

et al. 2023

Energy Fuels

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It is difficult to establish an effective injection production well pattern in tight reservoirs, and water injection huff-n-puff is an important technology for EOR in late elastic energy development. The water injection huff-n-puff is established with a three-dimensional physical simulation experiment. The boundary conditions are simulated by setting up a pressure buffer device. The injection and production processes of horizontal wells are simulated by prefabricated artificial fractures at the injection port. The variation laws of 29 pressure points and 130 resistivity points can be effectively detected. Two cycles of experiments with different injection volumes are carried out, the change process of pressure and resistivity is analyzed, and the oil production mechanism is described. The fluid transfer velocity along the fracture extension direction is higher than that in the vertical fracture extension direction. The effect of the first cycle of the water injection huff-n-puff is significantly better than that of the second cycle. The change rule of oil recovery and oil change rate with different injection volumes shows that there is an optimal injection volume to maximize the on-site implementation benefits. The experimental results provide a theoretical and experimental basis for EOR by a water injection huff-n-puff in tight reservoirs.

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Section: Introductionmentioning

confidence: 99%

Oil Production Mechanism of Water Injection Huff-n-Puff for Enhancing Oil Recovery in Tight Sandstone Reservoir

Ji,

Yu,

Liu

et al. 2023

Energy Fuels

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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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“…First, a certain volume of water is injected into the reservoir through a production well, then the well is soaked for a period of time, and finally, oil is produced through the production well. The feasibility of water huff and puff for tight oil reservoirs lies in the following: first, the water huff and puff technology does not require the ultrahigh injection pressure required for water flooding, and there will be no burst flooding between production wells and water injection wells; second, water huff and puff technology can effectively produce oil by using mechanisms such as energy enhancement, imbibition, and oil–water gravity differentiation. − Compared with energy enhancement and oil–water gravity differentiation, imbibition is a more complicated problem, and it is also a hotspot in the current research on the efficient development of tight oil reservoirs. − …”

Section: Introductionmentioning

confidence: 99%

The Law and Mechanism of the Sample Size Effect of Imbibition Oil Recovery of Tight Sedimentary Tuff

Yang

Dong

et al. 2022

ACS Omega

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Imbibition is an important mechanism to improve the recovery factor (RF) of a tight oil reservoir. Accurately evaluating the oil production capacity of tight oil reservoirs by imbibition is of great significance for the formulation of oilfield production plans and productivity prediction. However, there is currently no unified regulation on the selection of rock sample size in tight oil reservoir imbibition evaluation experiments, resulting in great differences in reservoir imbibition oil production capacity obtained from rock samples of different sizes, which brings great challenges to the efficient development of tight oil reservoirs. To clarify the law and mechanism of the rock sample size effect of tight core imbibition oil recovery, this paper takes the newly discovered tight sedimentary tuff (TST) oil reservoir as an example. First, several representative real cores were collected. Then, their wettability and pore structure characteristics were analyzed. Finally, physical simulation experiments of imbibition under different rock sample sizes were conducted. The results show that the TST has very favorable imbibition conditions, which are manifested in the following: (i) the wettability is weakly hydrophilic to hydrophilic; (ii) the mineral composition is tuffaceous minerals, calcite, and quartz, without clay minerals; (iii) micro-nanoscale pores are developed; and (iv) the pore throats are evenly distributed. In the imbibition experiments of rock samples of different sizes, the oil production characteristics of the core surface, the variation form of imbibition rate, pore production characteristics, and the influence mode of imbibition pressure on imbibition do not have the sample size effect. However, the RF of the spontaneous imbibition has an obvious sample size effect, and there is a good exponential function relationship between the imbibition RF and the specific surface area (SSA) of cores. The fundamental reason why the rock sample size effect of the TST imbibition oil recovery is relatively stable and has strong regularity is that its pore structure and wettability are relatively homogeneous and stable. The change of rock sample size does not have a great impact on the distribution of the core pore structure and wettability, resulting in no significant change in its imbibition power, resistance, and distance. Therefore, the main factor determining the imbibition RF of rock samples with different sizes is their SSA. The research results of this work can provide an important theoretical basis for understanding the law and mechanism of TST imbibition oil recovery and unifying the imbibition experimental results of small-sized rock samples.

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A modified embedded discrete fracture model to study the water blockage effect on water huff-n-puff process of tight oil reservoirs

Cited by 27 publications

References 31 publications

Oil Production Mechanism of Water Injection Huff-n-Puff for Enhancing Oil Recovery in Tight Sandstone Reservoir

Oil Production Mechanism of Water Injection Huff-n-Puff for Enhancing Oil Recovery in Tight Sandstone Reservoir

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

The Law and Mechanism of the Sample Size Effect of Imbibition Oil Recovery of Tight Sedimentary Tuff

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