| Because of poor reservoir properties, serious reservoir heterogeneity, complex gas-water contact and other factors, the development of T3x2 reservoir in Xinchang gas field was relatively poor. By the year of May,2014, except the well L150,formation water was found in the producing wells, among which the water production of well X2 was up to 320m3/d. From the distribution of production wells, the gas reservoir currently produces water. Although there was a water-free gas production period, it is obvious that the gas reservoir was invaded by water with strong energy.The predecessors’ research achievements are not enough to meet the development requirements of T3x2 gas-water reservoir in the future. Therefore, there is a strong need to study further gas and water distribution in T3x2 reservoir, which will provide evidence for the continuous development of billions of geological reserves.The study mainly focuses on the gas-water distribution of T3x2 reservoir. On the basis of previous studies, combined with data of the existing mud logging, core,logging, testing, water chemistry analysis, production performance etc. guided by the theories of development geology, logging geology, hydrogeology, reservoir geology,reservoir engineering etc, the paper carries on the research to identify the types of gas reservoir, the chemical characteristics of water, water producing type of individual well and reservoir gas-water distribution, finally reaching the following conclusions:1. The existing dynamic and static information of gas reservoir wells shows that the T3x2 reservoir of Xinchang field is tight sandstone gas reservoir, while there are also good gas reservoirs with high porosity and permeability.The gas mainly gathers in the high-quality reservoir, the highly developed large fractures and high-porous layers are the key factors for high and stable yield for production wells.2. According to the analysis of water chemistry, testing and dynamic individual well production data, the T3x2 reservoirs of Xinchang field can be divided into four categories: the remnant liquid by construction, condensate water, mixed water(formation water and condensate water) and formation water. Among which, the gas reservoir formation water chemistry characteristics are relatively stable, which is with high salinity and belongs to Ca Cl2. Mineralization degree of formation water changes in the development process due to the mixture of formation water and condensate water. Moreover, the early drilling and completion fluids also have some impact on the formation water mineralization, but mineralization degree of the formation waterfluctuates in a certain range.3. By analyzing pressure data, formation water chemistry data, production testing data as well as production performance data, using dynamic and static methods, gas reservoir can be divided into three fracture units: Unit X856, Unit L150 and Unit X10.Unit X856 contributes most(83.86%) to total production.4. According to the change characteristics analysis of the gas-water production wells, all the gas wells are divided into 3 kinds: less affected by the formation water gas wells, general water invasion gas wells and special gas-water production wells.Under the initial condition, gas gathers in the high part of fracture unit, and the lower portion is occupied by the formation water. Water and gas coexist in the fracture unit.The characteristics of special gas-water production wells have proved the existence of gas-driven water model by compartment-gas.5. By using material balance methods, we calculate the geological reserves of unit X856 to further predict the influx water volume and the corresponding water volume. Combining reservoir prediction results, it shows that there is no contiguous large body of water in the gas reservoir, the gas and water distribution is mainly the gas-driven water model by compartment-gas. This explains the anomalies that the small body of water in gas reservoir has high energy.6. Currently the Xinchang Gas field is with high formation pressure, especially in the X856 fracture system, which can rely on natural energy for drainage. When the natural energy drops and it becomes hard to produce, other measures can be taken to help with the drainage. It is recommended that on the basis of producing with drainage system of X201 and X2, gas wells on the lower parts of the river like CX560 and CX565 can be used to carry out strong drainage. Through the drainage well CX565, the flooding of X3, X865 and X853 is expected to be solved, and gas production capacity can be increased to ultimately improve the gas reservoir recovery. |
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