Open-hole multistage completions (OHMS) were found to outperform cemented liners with plug-and-perf stimulation in Bakken wells, according to a paper presented at the SPE Annual Technical Conference and Exhibition in Florence, Italy, this week. The paper was co-authored by Slawson Exploration and Packers Plus Energy Services.
The cemented liner with plug-and-perf diversion and the OHMS are the two primary completion methods currently used in the Bakken for multistage hydraulic stimulation, Josh Jany, Packers Plus, explained in his presentation. With the cemented liner/plug and perf method, common problems include remedial operations resulting from stuck plugs/guns; insufficient bond through the horizontal lateral; and premature setting of bridge plugs.
Additionally, in order to ensure that all residual proppant in the lateral are cleared out after the fracture of that stage is complete, each stage must be flushed with at least two stage volumes. This could raise could concerns with near-wellbore conductivity because “we are effectively overflushing the fracture for each stage,” Mr Jany said.
For this paper, Mr Jany and his co-authors looked at three wells with cemented liner/plug-and-perf completions and 13 wells in the same field with OHMS. Open-hole multistage completions were found to outperform the cemented liner over the study period of 210 days, with OHMS wells having 58% higher initial production (IP) rates. This trend continued with the average 30-day and 60-day production rate values, with OHMS wells having 48% and 57% higher rates, respectively.
Recently, new high-density technology has allowed operators to double the number of stages on Bakken wells, Mr Jany said, thereby maximizing reservoir contact. Looking at 10 wells with nine-stage completions and 13 wells with 18-stage completions, the authors found a 79% increase in average daily IPs, 88% in 30 days and 83% in 60 days for the 18-stage completions.
“By doubling the number of stages in a particular lateral, we were able to basically double our production,” he said. “The question is, if you double the number of stages and you get essentially double the production, are you improving your EUR (estimated ultimate recovery) or are you just extracting the hydrocarbons at a faster rate?
“We like to believe that you improve your EUR because have more access to the reservoir itself.”
The high-density liners do bring additional concerns that must be addressed in operations and planning, Mr Jany said. “With tighter spacing on the production liner, we have an overall increased rigidity of the liner itself. In some cases, it makes it more difficult to navigate through dogleg severity associated with the lateral. Centralizers can significantly offset this with the right material selection, blade orientation, the number of centralizers deployed.” Hole conditioning also becomes paramount, he added.
Mr Jany commented, “We’ve completed numerous wells with 22 stages with very promising results. Due to operational efficiencies, we actually dropped it back to 19 as of late. We’re trying to find the balance between what’s best in terms of ultimate recovery versus what’s most consistent and effective on a day-to-day basis with operations.”
SPE 135584, “Next Generation Multi-Stage Completion Technology and Risk Sharing Accelerates Development of the Bakken Play,” by Matt Houston and Mark McCallister, Slawson Exploration; and Josh Jany and Josh Audet, Packers Plus Energy Services, was presented at the SPE ATCE, Florence, Italy, 19-22 September 2010.