科研之友
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摘要
Development of unconventional tight oil and gas reservoirs is an unsolved problem in the energy industry due to the low productivity of oil and gas wells. The reason is the low permeability of reservoir rocks that are very vulnerable to the contamination of the water in the drilling and fracturing fluids. Although gas-drilling (drilling with gas) has shown to be promising to solve the problem, several problems hinder its application. These problems include formation water influx, wellbore collapse, excessive gas volume requirement, and hole cleaning in horizontal drilling. A new technique called gas lift drilling has been proposed to solve these problems. A technical assessment of gas-lift drilling was carried out in this study to determine the feasibility of the newly proposed drilling technique. It is found that, compared to conventional (positive circulation) gas drilling, gas-lift drilling can reduce gas injection rate required for hole cleaning by at least 70%. The kick-off pressure for unloading the well depends on water zone pressure and valve setting depth, and can be lowered by reducing valve spacing. The gas injection pressure in gas-lift drilling will be in the same level as in the conventional gas drilling. Mathematical modeling shows that the temperature profiles in the annulus and inside the drill string will be significantly higher than the geo-temperature profile. The gas-lift valve can be designed to open and close automatically depending upon the water-induced pressure inside the drill string. The gas-lift valve design experience gained from gas-lift operations in oil production can be employed in gas-lift drilling. In this paper, it is concluded that gas-lift drilling has the potential to become a viable and feasible technique for development of unconventional tight oil and gas reservoirs with improved performance and reduced cost.
- 出版日期2017-1
- 单位中国石油大学（北京）; 西南石油大学
