| The Maokou formation in Hejiang Structure located in south of Sichuan area is a kind of water-carrying gas reservoir, which uses karst cave as main reservoir space and crack as major seepage channel. Most wells are fractured as a separate system, and has the characteristics of gas and water in the same layer, the relationship between air and water is quite complex, and that makes the gas reservoir production a very tough job. In the process of Hejiang gas reservoir, the spilling of gas reservoirs has brought a series of problems, seriously hampered the development of gas reservoir, and it also reduces the recovery efficiency.This paper take gas reservoir geological characteristics and development dynamic characteristics both in to consider, and based on drilling, logging, recording, testing and production material of Hejiang structure, combined with previous research in the region, make detailed analysis on geological model of reservoir , reservoir development characteristics, dynamic characteristics of gas production, gas-driven energy, gas and water distribution, etc. Recognition water reservoir reserves calculation method, summarize the influence factors of drainage, provide basis for potential force for gas reservoir development. Now achieve the following understanding:1. The main gas reservoir driving energy is trap-type gas drive, the main driving force of the large number outputs to water bodies within the system. According to gas-water production characteristics, watered-out oil wells in the study area can be divided into three types: water rapid increasing (water vapor), stable and decreasing type.2. The influence elements of Dug wells water reserves including: the degree of development, reservoir permeability, reservoir borehole location, separate gas and water production measures. In the production process, use or create favorable conditions for water drainage is the most practical way to improve recovery efficiency.3. Parts of fracture-cavity systems in study area are with high water output.In order to solve the problem of small calculation results caused by traditional pressure drop method, we use the material balance method to calculate the reserves. By the example calculation of three fracture-cavity systems in Hejiang structure, the reserves increased by nearly 7 million.4. It has been divided the favorable distribution areas of remaining reserves in Hejiang structure, and have proposed new measures of potential tapping. Firstly, strengthening drainaging could be used to find out the separated gas in Well He30 fracture-cavity system. Secondly, new development well could be added in He31 well field to produce the separated gas directly. |
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