Optimization System of Coalbed Methane (CBM) Horizontal Well Types and Engineering Technology Modes in southern Qinshui Basin, China

摘要

To optimize the coalbed methane (CBM) horizontal well types in the southern Qinshui Basin, the optimization system of horizontal well types accompanied with corresponding engineering technology modes was established basing on the well type geology adaptability and key factors influencing the horizontal well productivity. Results show that, at present, two types of horizontal wells including single-(L and U) and multi-(V, herringbone and roof) branches are used in this basin. Under the targets of easier well completion, less pollution, and more benefit, the workflow of well type optimization is that: 1) determining the horizontal well development area with the coal structure; 2) extracting the vertical well development area by the vitrinite reflectance from the horizontal well development area; 3) determining the horizontal well types and engineering technology modes by considering the ratio of critical desorption pressure (p_c) to initial reservoir press (p_i) and in situ stresses. Seven engineering technology modes are put forward, namely production by vertical well with fracturing, joint production by vertical well with fracturing and horizontal well with staged fracturing, joint production by single- and multi-branch horizontal well with cave completion, production by multi-branch horizontal well, joint production by vertical well with fracturing and single-branch horizontal well, production by single-branch horizontal well with cave completion, and no production at the current stage.