Abstract
More than 80% of gas reservoirs in the four major gas provinces in China (Changqing, Southwest, Tarim and Qinghai) are producing water, and the gas reserves involved account for more than 75% of the total.
On the basis of continuous monitoring of water production and deliquification techniques in the provinces, the following observations are achieved. Firstly, the severity of water production in the four provinces is getting increasingly higher, and big challenge is confronted in striving for stable gas production in the fields. The proportion of water-producing wells increased rapidly from 38.1% in 2011 to 49.7% in 2018, resulting in dramatic decrease in single-well gas production (by 20% -- 99%). Secondly, deliquification is the primary technique for stable gas production and improved gas recovery in water-producing gas fields. The number of wells where deliquification technique is applied accounts for 94.68% of the total gas producing wells. The incremental production by deliquification accounts for 63.56% of the total increment. Foam deliquification is the major deliquification process applied in the four provinces. In 2018, the number of wells where foam deliquification was applied accounted for 66.43% of the total number of wells with deliquification, and the incremental production accounted for 55.20% of the total increment by deliquification. The techniques such as plunger lift and velocity string deliquification are also being applied more and more.
Three new problems are identified with deliquification techniques in the four provinces at present. Firstly, with the maturing of the fields, there will be more and more strippers with some of them approaching to the end of their life, and foam deliquification will no longer be competent as the major deliquification process. Secondly, as a deliquification process for strippers, plunger lift has a big potential of wide application, but there are still many problems to be solved with it. It is urgent to systematically monitor and analyze its performance, with proposals to be put forward on the relevant researches and its dissemination. And thirdly, Tarim gas field is facing the fact that water production gets more and more serious, and the gas production is drastically decreasing. What is even worse, the current method has poor effect on water control, so it is urgently imperative to carry out comprehensive studies on water production and overall water-control countermeasure.
By literature investigation and on-site analysis for nealy a decade, it is found that the operation parameters of 33% of the strippers fall beyond the applicable range of foam deliquification. The effective solution to this problem is to disseminate the application of plunger lift to meet the constantly increasing demand because of more and more wells' deteriorating to be strippers.
