Best Practices and Lessons Learned in Deploying and Setting Dissolvable Frac Plugs in Middle East at HPHT Conditions

Abstract

The multistage hydraulic fracturing technique is considered to be one of the most effective stimulation techniques used for exploiting unconventional plays. The use of dissolvable frac plugs in multistage hydraulic fracturing has the potential to reduce well intervention requirements. Applicability of dissolvable frac plugs, as an integral part of plug and perf operations, in Middle East unconventional plays presents a myriad of technical challenges associated with high-pressure and high-temperature (HPHT) well conditions. Two counteracting drivers coexist in dissolvable frac plug design: 1) The need for the frac plug to withstand well conditions during the entire frac stage operational cycle and 2) the requirement for the frac plug to dissolve as quickly as possible after the stimulation treatment has been placed. The HPHT conditions of the wells utilizing dissolvable frac plugs adds to the complexity of not only the plug design, but also its associated deployment operational procedures. The main premise of the functional methodology of dissolvable frac plugs involves a chain reaction being triggered in the presence of specific fluids under specific temperature conditions. After the commencement of the degradation/dissolution chain reaction process, the useful lifetime of the frac plug begins to deplete, where the degradation chain reaction accelerates with increasing temperature exposure. Site operations will then conform to expedited practices to minimize undesired exposure time. This would minimize the risks of degradation/dissolution before plug setting, plug test, and actual stimulation treatment placement. Based on the HPHT well conditions of Middle Eastern unconventional plays, a structured process was put in place to satisfy the define, assess, select, and execute phases of the initiative The inevitable occurrences of unforeseen complications during operational deployments served to accelerate the learning curve for the continued utilization of dissolvable frac plugs. Operational issues ranging from electric line unit complications to frac pump downtime during the initial frac plug deployments compromised the structural integrity and functionality of the dissolvable frac plugs. Recognizing that exposure time was critical to maintaining the structural integrity of the plug, best practices were derived and enforced to minimize said exposure time. In addition, slight design modifications were made to specific components of the plug to increase its robustness while not compromising the desired degradation rates. The adoption of these mitigating measures has resulted in the acceptance of the dissolvable frac plug as the standard plug option for all plug and perf operations. The vast experience gained during the deployment of more than 1,000 dissolvable frac plugs for hydraulic fracturing stages in a Middle Eastern country has served as a basis to conceive a list of best practices to address mitigating unforeseen complications. These best practices are enforced to minimize plug exposure time, which in turn maximizes the probability of plug utilization success.