Effects of Well Placement Timing and Conductivity Loss on Hydrocarbon Production in Multiple Hydraulically Fractured Horizontal Wells in a Liquids-Rich Shale Play

Abstract

Abstract Horizontal wells in liquids-rich shale plays are now being drilled such that lateral and vertical distances between adjacent wells are significantly reduced. In multistacked reservoirs, fracture height and orientation from geomechanical effects coupled with natural fractures create additional complications; therefore, predicting well performance using numerical simulation becomes challenging. This paper describes numerical simulation results from a three-well pad in a stacked liquids-rich reservoir (containing gas condensates) to understand the interaction between wells and production behavior. This paper discusses the use of an unstructured grid-based numerical simulator that incorporates complicated geometries of both hydraulic and natural fractures. It can handle compositional simulation to better model gas condensates with special focus on timing of third well placement and the loss of conductivity effects on production from these wells. A base case was created with a stacked shale play containing three parallel wells but with staggered elevations. Variables used in this study include matrix permeability, condensate-to-gas ratio (CGR), fracture length, well staggering, time of well placement, conductivity degradation, and presence of natural fractures. Simulation runs were conducted for a five-year duration. More than 20 compositional simulation runs were conducted. For the base case, staggering resulted in a slight decrease in both cumulative oil and gas production compared to a case without staggering. Matrix permeability had the most dominant effect on both oil and gas production. Fracture and matrix conductivity losses were more detrimental to cumulative gas production than oil production. For the limited cases studied, placement of the third well one year after the first two wells began producing resulted in a spike in both oil and gas production from the pad. This produced cumulative oil and gas amount was close to that of three wells producing simultaneously, especially if fracture half-lengths for the third well were the same as the first two. However, cumulative oil and gas production reduced significantly if fracture half-lengths were smaller than the other two wells. When all wells experienced significant conductivity loss, gas production was affected more than oil production when the third well was placed one year after the first two wells began producing. In all cases, placing the third well between the other wells was helpful in increasing overall production from this pad. Natural fractures increased both oil and gas production in the cases studied. This paper addresses important issues associated with a liquids-rich unconventional play. It demonstrates successful use of unstructured grid-based reservoir simulation modeling to address well placement timing, well staggering, conductivity damage effects, natural fractures, hydraulic fractures not perpendicular to the wellbores, and several other important issues for which little is known so far. Results from this study type can be used to make important decisions regarding well placement and timing in a multiwell setting.