Optimization of Multiple-Fractured Horizontal Tight Gas Well

摘要

Horizontal drilling and hydraulic fracturing are two reliable technologies which have made recovery of tight/shale gas economically viable. A common practice is to drill horizontal well parallel to the minimum horizontal stress, consider short perforation intervals and hydraulically fracture the formation. It is expected that the created fractures would be perpendicular to the horizontal well (transverse fractures). Determining the number of fractures in such horizontal wells is of great interest by the industry. Although one may assume that the more the number of fractures the better the productivity, there is always an optimum number of fractures (hence optimum fracture spacing) which is obtained based on both production rate of the reservoir and its cumulative production. In this paper, different sensitivity analyses on physical optimization parameters are combined by economical evaluation to find the optimum value of fractures spacing (number of fractures), and the length of horizontal section. These optimization analyses have been done on horizontal section length, total permeability, anisotropic permeability ratio, and drainage area. Analyses have been performed based on the values of gas production rates, cumulative production, and defined K value. Finally, economical optimization which was performed using U.S. historical monthly gas prices, inflation and interest rates over a period of 27 years, was coupled with production data obtained from modeling. All the costs and revenues were converted to U.S. Dollar value in 2009. This evaluation shows that for each specific reservoir an optimization study is required and there is no unique solution for all types of reservoirs. However, the gas price forecast is the main factor which governs the whole optimization process.