Water producing mechanisms of carbonate reservoirs gas wells: A case study of the Right Bank Field of Amu Darya, Turkmenistan

The mechanisms of carbonate gas reservoirs were systematically studied with the Right Bank Field of Amu Darya Gas Field, Turkmenistan, as an example. Water produced from the reservoirs has three sources, condensate water, engineering fluids and formation water. The fluid physical property and water-gas ratio (WGR) method for the single component conditions and the chloridion conservation method for the multi-components conditions were established to identify the components contained in the production fluids. A water production diagnosing curve, which refers to the degree of reserve recovery as a function of the water-gas ratio in the log-log coordinate curve, was then established and the formation water producing wells were divided into three patterns, i.e. Type 1, Type 2, and Type 3. Through in-depth studies of the static and dynamic reservoir characteristics of each pattern, the following understandings were attained: The reservoirs of Type 1 are mainly porous, and the water producing mechanism is bottom water coning along matrix pores; the reservoirs of Type 2 are mainly fractured-porous, and the bottom water produces basically through the natural fracture system; the reservoirs of Type 3 are mainly fractured-cavity, and the bottom water produces basically through large-scale fractures and caves.