Novel Approach to Mitigate Gas Production in a High GOR Carbonate Reservoir With Drilled Wells—Case Study

Abstract

Improving oil production is one of the most challenging subjects in carbonate reservoirs, especially in the case of thin formations when reservoir pressure is close to saturation pressure with undesired well locations. In this study water injection was used to mitigate gas production in a thin reservoir with high gas oil ratio for the purpose of optimizing oil production. The studied field is a cretaceous oil bearing reservoir composed of tightly packed limestone characterized by high porosity but poor permeability with a thickness of 55-65 meters throughout the reservoir. The matrix permeabilities and porosity are in the range of 0.01-150md and 5-35 percent respectively. The oil gravity is 21.5 degree API and reservoir pressure of 1700psia which is close to bubble point pressure of 1492psia. The produced wells were drilled in top layers of the reservoir. A full field model was constructed to determine the optimal production strategy and applied reservoir management with available produced well locations. Two possible scenarios; namely, natural depletion and water injection were compared. Results indicated that water injection yields better recoveries than natural depletion. Different scenarios of injection well location, well orientation and mechanism of injection were considered. Horizontal injection and production wells located at same layer were found to maintain reservoir pressure, prevent gas production, and increase oil recovery. Depleted regions near the producers were found to play a major rule on the success of the project. The enhancement of oil recovery was improved to 37 percent in the case of water injection with the implementation of proper reservoir management.

Characteristics of multiscale mass transport and coordination mechanisms for shale gas

“…(2) 压裂液的低返排率和钻井完井过程中的工作 液侵入所造成的水相圈闭损害 [40,41] , 一定程度上制约 了页岩气的最终产出能力 液侵入速度. 根据Gallegos等人 [43] 对2014年美国数千口 页岩气水平井的统计, 水力压裂过程中进入储层中的 平均液量为19425 m 3 , Horn等人 [44] 的统计表明, 美国 页岩气井的压裂液返排率通常介于35%~62%, 而Che-kani等人 [45] 的分析认为页岩气井的返排率更低, 通常 http://engine.scichina.com/doi/10.1360/N092017-00202…”

Impact of Aqueous Phase Trapping on Mass Transfer in Shales with Multiscale Channels

“…To obtain economical production, it is crucial to drill a horizontal well and implement multistage hydraulic fracturing to form a complex fracture network and to increase the contact area between the fracture surface and matrix. − Although the characteristics of fracturing fluid flowback among different shale reservoirs are not the same, the flowback efficiency of a shale gas well is generally low. A large amount of retained fracturing fluid in a shale reservoir not only have a significant influence on gas flow, which greatly restricts the reservoir stimulation effect, − but also induce potential contamination of groundwater. , Formation damage caused by fracturing fluid retention is mainly reflected as aqueous phase trapping (APT) damage . The formation process of APT damage could be divided into three main stages: (1) at the initial stage, the external aqueous phase has not entered the reservoir yet.…”

Experimental Investigation on Imbibition-Front Progression in Shale Based on Nuclear Magnetic Resonance

“…Compared with hydraulic fracturing in conventional reservoirs, hydraulic fracturing in shale reservoirs is characterized by the low flowback efficiency of fracturing fluid, thus resulting in the retention of large amounts of fracturing fluid in shale formation . After investigating large amounts of production data on shale reservoirs, it is found that the flowback efficiency of the fracturing fluid is only between 10% and 40%. , The retarded fracturing fluid significantly increases the water saturation in the vicinity of the fracture surfaces, thus resulting in the blockage of gas flow and reduction of postfracturing productivity. When water saturation is close to 40%∼50%, gas well production will be seriously damaged .…”