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[31013-24-09] Gas reinjection to improve oil recovery in a rectangular gas cap oil reservoir
Chairman: Suwat Athichanagorn （Chulalongkorn University）, Min Xiabo (Central South University)
Keywords:GAS REINJECTION , GAS CAP RESERVOIR, VERTICAL WELL, HORIZONTAL WELL, FRACTURED HORIZONTAL WELL
Conventional improve recovery of a gas cap reservoir commonly involves the reinjection of produced gas back into the reservoir to initiate compositional interactions between oil and gas which mostly results in either stripping or swelling effects thereby causing trapped oil to become mobile.
This method of improve recovery depends on a wide range of parameters some of which include the location of the producing/injecting well, the well type, the oil withdrawal rate and the size of the gas cap.
In this study, gas reinjection process into a consolidated sandstone oil reservoir is performed. The reservoir was constructed as a rectangular and homogenous oil reservoir model, and simulated using a compositional reservoir simulator.
The effects of operational parameters including production rate, well completion type, gas reinjection time and level of pressure maintenance by gas reinjection were studied, with the outcomes compared with the results of natural depletion of various cases.
The results showed that producing the reservoir at lower rates is very efficient than producing at higher rates, this is attributed to the fact that at lower oil rates, the effects of gas cap coning into the production section of the wells is much lower than at higher rates, with the gas-oil contact expanding rather uniformly, preventing early gas breakthrough and keeping the reservoir pressure sufficiently high for longer periods of time. In terms of well completion types, horizontal well completion gives higher oil efficiency than vertical well and fractured horizontal well all producing under natural depletion conditions and equal conditions of flow rates. In terms of gas reinjection into the reservoir, the vertical wells under gas reinjection schedule give close to 3 times more recovery efficiency compared to vertical wells under natural depletion, while horizontal wells under gas reinjection schedule gives about 2 times more recovery efficiency compared to horizontal wells under natural depletion at equal production conditions.
The results thus shows that employing appropriate parameters and conditions could lead to very much improved recovery by gas reinjection.
This method of improve recovery depends on a wide range of parameters some of which include the location of the producing/injecting well, the well type, the oil withdrawal rate and the size of the gas cap.
In this study, gas reinjection process into a consolidated sandstone oil reservoir is performed. The reservoir was constructed as a rectangular and homogenous oil reservoir model, and simulated using a compositional reservoir simulator.
The effects of operational parameters including production rate, well completion type, gas reinjection time and level of pressure maintenance by gas reinjection were studied, with the outcomes compared with the results of natural depletion of various cases.
The results showed that producing the reservoir at lower rates is very efficient than producing at higher rates, this is attributed to the fact that at lower oil rates, the effects of gas cap coning into the production section of the wells is much lower than at higher rates, with the gas-oil contact expanding rather uniformly, preventing early gas breakthrough and keeping the reservoir pressure sufficiently high for longer periods of time. In terms of well completion types, horizontal well completion gives higher oil efficiency than vertical well and fractured horizontal well all producing under natural depletion conditions and equal conditions of flow rates. In terms of gas reinjection into the reservoir, the vertical wells under gas reinjection schedule give close to 3 times more recovery efficiency compared to vertical wells under natural depletion, while horizontal wells under gas reinjection schedule gives about 2 times more recovery efficiency compared to horizontal wells under natural depletion at equal production conditions.
The results thus shows that employing appropriate parameters and conditions could lead to very much improved recovery by gas reinjection.
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