Application of Short-Radius Horizontal Boreholes in the Naturally Fractured Yates Field

Abstract

Summary This paper discusses the performance and simulation of short-radius horizontal boreholes being used in the Marathon-operated Yates Field Unit in west Texas to minimize drawdown and therefore to reduce gas and water coning in a thin oil column. Yates is a very prolific field with extensive fracturing and high-quality reservoir rock. Superimposed on a high-density orthogonal fracture network are widely spaced regional joints with a strong directional tendency. Major questions are how these directional joints affect the horizontal-well performance and whether wells should be drilled parallel or perpendicular to the joints. Dual-permeability reservoir simulation studies were performed to study optimum orientation of the borehole with respect to the natural fracture network. Additionally, optimum well-completion elevation was studied. Forty-six vertical wells have been recompleted as short-radius horizontal boreholes since 1986. The large productivity increase of the horizontal boreholes compared with the previous vertical completions indicates that the wells are intersecting the regional joints.