Abstract

Performance of conventional, steam-assisted gravity drainage (SAGD) horizontal well completions can be significantly impacted in formations with low vertical permeability and interbedded mudstone layers impeding vertical drainage. Also, because of shallow depth, caprock integrity, and/or thief zone issues, the lower operating steam pressure for SAGD completions can impact its ability to grow the steam chamber vertically in a timely manner. Such performance degradation results in lower production rates and often higher steam oil ratios. A vertical well injector/producer was proposed that consists of vertical, propped planes at varying azimuths installed from the bottom to the top of pay. Steam is injected at the top of the pay and liquids are extracted at the bottom. The well operates immediately in SAGD mode (i.e., the continuous injection of steam and the continuous extraction of liquids), resulting in peak production achieved within 30 to 45 days. Reservoir simulations show that the single-well SAGD system's performance is superior to a conventional SAGD completion, achieving greater than 2xNPV10 (net present value) of conventional SAGD in clean McMurray channel sand. Incorporating multiple vertical producer wells with a single central vertical SAGD injector/producer well, yields system performance far superior to a conventional SAGD completion, achieving greater than 6xNPV10 of a conventional SAGD completion in clean McMurray channel sand. The oil production rate for the vertical SAGD system with multiple producers is 4x faster than a conventional SAGD completion, with a greater recovery factor, and a lower cumulative steam oil ratio (SOR) of 1.5 compared to 2.5 resulting in a 40% saving in both Capex and Opex. Simulations of the system in variable geology, indicate that the vertical drainage efficiency of the system is virtually independent of geology, provided the multi- azimuth, high permeability propped vertical planes connect the wells hydraulically and are constructed continuously throughout the pay thickness.

You can access this article if you purchase or spend a download.