Analysis Of Water Discharge And Control Measures In Main Gas Reservoir Of M Gas Field

Nowadays, most of the gas reservoirs in China and abroad belong to different levels of water-drive reservoirs. Water invasion could suppress the gas well’s production capacity, increase the abandonment pressure and reduce the reservoir recovery. The research objects in this paper are the S gas reservoir and the BP gas reservoir, which are the main part of M gas field. And the research subject is based on the cooperation project of gas reservoir exploration and development at abroad of CNPC. Along with the gas field development construction continually expanding and production time increasing, water invasion problem gradually becomes the main factor to restrict gas reservoir development benefit. Therefore, around the core issue of water invasion problem of the main gas reservoirs, four aspects of research work have been carried out, which are the basic information of gas reservoirs, the gas well water output principle, the water invasion mechanism and the countermeasures of gas well. The main study contents completed are as follows:(1) The paper has emphatically studied four aspects of the main gas reservoirs, which are geological characteristics, gas/water bearing formation distribution characteristics, reservoir connectivity and development status at present. It has concluded that S porosity gas reservoir has the higher porosity-permeability with the normal tempreture-pressure system, weak edge-bottom water and uniform pressure system, and BP fracture-porosity gas reservoir has the lower porosity-permeability with normal tempreture system, high-ultrahigh pressure system and strong edge-bottom water. The interwell connectivity in the western block is better and the corresponding one between the eastern block and western block is poor.(2) On the basis of gas reservoir production performance data collection from2009to2014, it has reached the results that the main water source of S gas reservoir is condensate water and a part of the old wells have been water loading. As for the BP reservoir, the gas-producing wells currently locate in the west block and have a stable production. Water-gas ratios of the ones near the large faults have showed a trend of rapid rise. The wells in the eastern block have been shut down due to severe water-yielding problem. Water invasion problem has been seriously affected the gas reservoir production. The water sources include five categories, which are condensate water, original mobile water and secondary mobile water, edge and bottom water and working fluid backflow. Gas well water-producing principle of the main gas reservoir has been analysed and divided into four types, which are low-yielding stable-water, low water-slow growth, the middle-water rapid growth and high-yielding water-rapid growth combining with typical wells’dynamic production performance and the water-gas ration change features of gas wells. Then it has analysed the gas well water loading forming mechanism and summarized the effective diagnosis methods. Based on the principle of highest prediction success rate within the common liquid-carrying critical flow rate models, this paper has finally chosen Li Min model and Belfroid model to make the diagnosing chart.(3) According to the reservoir seepage law and analysis of main influence factors of water invasion, the sensitivity analysis has been conducted utilizing the the ideal gas reservoir water invasion mechanism model established by the Eclipse numerical simulation software. The result indicates that the fracture system is the major determinant factor for the fracture-pore reservoir, water energy is the key to determine gas reservoir water invasion activity, gas recovery rate is the main means to control water invasion and the effect of horizontal section length and water avoidance height on gas reservoir water invasion is larger. Furthermore it is preliminarily believed that the main gas fields mainly have three water invasion types:water coning, vertical water channeling and vertical channeling-lateral invading ones.(4) According to gas reservoir current production performance, the paper has separately put forward corresponding countermeasures for the reservoir and single well under the guidance of gas well water-producing principle and sensitivity analysis conclusions.Through the research in this article, there has a more fully understanding of gas well water-producing principle and the gas reservoir water invasion mechanism. The water-controlling countermeasures are of great significance in finally realizing the production stability of the main gas reservoir of M gas field, which provides references and assistance to develop similar gas reservoirs.