The Evaluation And Optimization Of The Development Program For The Volcanic Gas Reservoir In Xushen Gas Field

The volcanic gas reservoir of Xushen gas field has currently become the main layer to enhance the gas production in Daqing oil field. But in volcanic reservoir lithofacies are complex and changeable, the reservoir is dense, the heterogeneity is extremely strong, micro cracks and bottom water are developed, and the production interval is big, so it is a world-class problem to develop it. How to make the correct development technology policy and the high quality, first-class development plan, is very important to the efficient gas development. According to the concrete characteristics of volcanic rock reservoirs, multidisciplinary joint tackling is used to overcome the difficult in volcanic reservoir description, reservoir productivity evaluation, single well production increase, and other bottlenecks technology, the development of the volcanic reservoir in Xushen gas field is also evaluated and optimized.The study of geology is the basis to develop gas fields, reservoir fine description is the key to make the development program well. Through the field outcrop fine description, target layer continuous coring and dense pattern anatomy to establish identification methods of volcanic rock lithology and lithofacies. The imaging logging, pre-stack and post-stack seismic material are studied to predict the distribution of crack-developing zones. Through the CT, NMR, constant speed pressure mercury and other special analysis techniques, the development characteristic of internal volcanic cracks, the micro cracks and stomatal cave is studied. To predict the showings of gas, the seismic inversion technology is used. On this basis, the description method of volcanic reservoirs has been established, which can improve the accuracy of the volcanic reservoir prediction. Geological characteristics of Xushen 1 block are as follow, Outbreaks phase and the overflow phase are the main lithofacies in the first member of Yingcheng formation; Reservoir space is composed by porosity and cracks mainly with high angles, the water mainly distributes under the gas and it is a tectonic lithologic reservoir. The whole reservoir is a large scale conventional dry gas reservoir with low porosity and low permeability.Two testing mode are producted, one is modified isochronal testing and the other is back pressure test. Reasonable work system has also been made. All these are based on the application of the testing, the analysis of the pilot production data and the well test interpretation. The productivity characteristic and the factors influence the productivity are uncovered, reasonable policy to develop the reservoir is also determined. On the basis of reservoir adaptability analysis, the advantages of the application of horizontal wells in volcanic reservoir are confirmed, the method for the horizontal wells optimization is conducted, the effective development mode for this kind of reservoir is explored, the productivity of single well,the level of the reserves producing and the overall benefits in volcanic reservoir are improved.On this basis, by the application of system engineering theory and method, programs of the geology, reservoir engineering, drilling engineering, production engineering, surface engineering and the relationship among them are determined, the system optimization process of the overall development program is conducted, the program is evaluated and optimized by dynamic evaluation method.38 wells are set in irregular pattern, annual gas production is 7.9×108m3, the gas producing rate is 2.55%,the stable production period is 10 years, the used gas in place is 311.3×108m3, the recovery is 42.1% after 20 years. The project is economical, the financial internal rate of return is 18.1%, the net present value is 356.328 million, the investment payoff period is 7 years. The risk of the program must be analyzed by the probability analysis and prevent and control measures must be conducted.At present, the program has been implemented smoothly and the effect is good development. The scientific proof to the reasonable and effective development of Daqing volcanic reservoir has been provided by this research and the development of foreign similar volcanic gas reservoir can be guided by this research too.