Optimized Production in the Bakken Shale: South Antelope Case Study

Abstract

Focused modifications in drilling, reservoir, and completion engineering from 2009 to the present have improved Bakken, specifically the South Antelope Field, production as much as 50% to 75%. To achieve these results, Helis Oil and Gas Co., LLC formed a multi-disciplinary team in 2008 which it tasked with evaluating and overhauling its completion approach. Pre-2008 completions followed conventional wisdom: target the Middle Bakken Formation between the Lodge Pole and the Three Forks Formations. Pre-2009 wellbore constructions included "kick outs" (i.e., multi-lateral), open-hole completions; short laterals; single-stage ported subs; sliding sleeves; and long stage intervals and were erratic and inconsistent. The designs and procedures resulted in a high percentage of pre-mature screenouts. In addition, the production responses on these Middle Bakken completions averaged 330 bopd with an estimated ultimate recovery (EUR) of 300 MBOe. During the pre-2009 period, 3 Three Forks were completed and these wells produced on average 550 bopd. After evaluating the pre-2009 results, the team recommended 10 changes: (1) change landing target to the Three Forks; (2) increase lateral lengths ~2x from "640's" to "1280's"); (3) increase formation contact (completion method, stage lateral length and, perforation spacing/density); (4) refine pump-down operations; (5) implement critical fracturing mechanisms diagnosis; (6) incorporate proppant selection (ceramic versus sand); (7) refine flush procedure to include monitoring and assure consistency; (8) integrate on-site, real-time pressure management and proppant schedule including proppant slugs, altered mesh types, and adjusted ramp schedule; (9) adjust treatment fluid design (25-lb gel loading instead of 40-lb gel loading); and (10) implement flowback and flowrate control. Implementing these recommendations, Helis deviated from conventional Williston Basin philosophy and drilled 30 "1280's" in 2010-2012. These wells resulted in ~1,500 bopd with a maximum of 2,500 bopd and EUR's of ~1,200 MBOe. They are among the best wells in the Williston Basin. In comparison, direct offset well EUR's averaged less than 750 MBOe. The success of these wells is not the result of one breakthrough but rather the result of sound changes to engineering techniques that were carried out systematically. Applying these engineering practices, maintaining strict adherence to recommended practices, and not making drastic, unfounded changes ultimately optimized production in this Bakken project.

CO2 injection for enhanced oil recovery in Bakken tight oil reservoirs

“…The Bakken formation with multiple oil-bearing layers is one of 55 major productive tight oil reservoirs in North America (see Fig. 1) 56 [1], where Middle Bakken and Three Forks are the two primary lay-57 ers for oil production since they have the best reservoir qualities 58 such as porosity and oil saturation [2]. It has been reported that 59 the Middle Bakken has an estimated average oil resource of 3.65 60 billion barrels and Three Forks has an estimated average resource 61 of 3.73 billion barrels [3].…”

CO2, Water and N2 Injection for Enhanced Oil Recovery with Spatial Arrangement of Fractures in Tight-Oil Reservoirs Using Huff-‘n-puff

“…The main objective of fracturing is to reconstruct the reservoir seepage formation and to achieve the purpose of the effective expansion and development of the fracture through the mechanical mechanism and provide a more efficient and convenient flow channel for the crude oil [2,7]. However, according to the evaluation of the oil production of tight reservoirs both in China and America, the production rate of tight reservoirs decreases rapidly, without a long and stable production period [2,6,[8][9][10][11]. Thus, it is difficult to obtain satisfactory oil recovery only relying on the depressurization process even with fracturing.…”

Simulation Study of CO2 Injection in Tight Oil Reservoirs

“…The Bakken formation with multiple oil-bearing layers is one of major productive tight oil reservoirs in North America [1], where Middle Bakken and Three Forks are the two primary layers for oil production since they have the best reservoir qualities such as porosity and oil saturation [2]. Figure 1 presents the location map of the Williston Basin with structure contours [3].…”