This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 218081, “Targeted Acid-Stimulation Technique for Production Enhancement: A Montney Case Study,” by Fraser T. Smith, SPE, StimStixx Technologies, and Zan Ramji, Prairie Thunder Resources. The paper has not been peer reviewed.
A safe and cost-effective method of stimulating a multizone hydrocarbon-producing well is presented wherein a tool containing dry chemical is deployed downhole by wireline. An extended exothermic reaction is initiated downhole that generates acid vapor at a target depth in front of the perforated interval, allowing each interval to be treated uniquely with specific acid blends. This method of acidizing has supplanted the previous method because of its sustained production enhancement and cost-effectiveness.
An operator’s field of mature oil-producing wells experienced steadily declining production. The typical well had two unique intervals, one being in the Worsley dolomite and the second in the Worsley siltstone. As part of a pilot project to investigate alternative stimulation techniques, the operator acidized the wells by deploying a downhole tool that generated acid in a vapor form in situ. The tools were deployed on wireline and placed in front of the perforated interval. Once at depth, a current was sent to the tool to initiate a chemical reaction, with the reaction products being acid gas as either hydrochloric acid (HCl) or HCl/hydrofluoric acid (HF).
Because the first pilot well yielded positive results, the Montney, found below the two existing intervals in the Worsley, was targeted. New perforations were shot over a 6-m interval in the Montney. The two existing intervals, in addition to the new Montney interval, were acidized and showed a sustained increase of 1,097%. A third pilot well was planned to be treated in the same way, but fill in the bottom of the well prevented the wireline from being shot in the Montney and only the two upper intervals were stimulated.
Based on this pilot project, six other candidates in the field were identified for treatment using the same approach and a workover campaign in November and December of 2022 was planned.
This treatment process featured various benefits. The primary driver was the efficiency of acidizing by using tools deployed by wireline. The wireline unit was on location to perforate the wells; however, it also could be used to acidize the wells by using the same equipment immediately after perforating. No added costs of having to mobilize a pump truck, acid haulers, and auxiliary equipment existed. The logistics also were greatly simplified because of the reduction of equipment and personnel on location. The tools were mobilized in a crate in the box of a pickup, typically with two operators.
A key benefit was a substantial improvement in the risk profile from a health, safety, and environment (HSE) perspective. Because the acid is generated only once the tool is downhole and placed in front of the zone of interest, no live acid is handled at surface. This presents less risk to operational staff and eliminates the need for equipment such as safety showers. Finally, the wells were able to be put back online faster than conventional methods because the wells did not require flowback.
