Optimization of Development Well Types for Low Permeability Carbonate Gas Reservoir

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As an important part of gas field development plan, the optimization of development well pattern is directly related to gas field development effect and economic benefit. Taking M gas field as an example, this paper focus on optimization of the reasonable development well types in low permeability carbonate gas reservoir from multiple aspects, such as reserves distribution, drainage area, production index and economic benefit. First of all, from the perspective of reserves distribution, considering the gas reservoirs of M gas field are vertically superposed and developed, the main reservoir MAWU 13 accounts for 41.6% of the total reserves of MAWU1+2 reservoirs which means that reserves advantage is not obvious. Thus the single-layer development of horizontal wells is not conducive to the effective recovery of reserves. Secondly, according to the percolation theory, the area replacement ratio model of horizontal wells and vertical wells is established. The research shows that when the drainage radius of vertical wells in M gas field is 1.3 km, the area replacement ratio of horizontal well and vertical well is 1.2. It is conveys that the controlled reserves of horizontal wells is only 1.2 times of vertical wells under the same reserves abundance. Thirdly, based on the production performance indexes evaluation of horizontal wells and their adjacent vertical wells in M gas field by rate transit analysis, the evaluation result illustrates that the development indexes of horizontal wells such as stable production capacity, dynamic reserves and cumulative gas production are not obviously better than vertical wells. Fourthly, by means of economic evaluation and gas well development index, The internal rate of return of horizontal wells is 11.2%, which is 4.2% lower than that in vertical wells under circumstances of investment of horizontal wells in M gas field is 3 times of vertical wells. Comprehensive research shows that, the development of vertical wells in M gas field is better to increase the degree of reserves production and economic benefit. This conclusion provides technical support for the beneficial development of low permeability carbonate gas reservoir.KeywordsFlow permeability carbonate gas reservoirWell typesArea replacement ratio of horizontal well and vertical wellCumulative gas productionInternal rate of return