Saudi Aramco Unconventional Production Engineering Division currently performs multistage propped fracturing operations using cemented plug and perf completions, to target tight gas reservoirs requiring stimulation. To improve operational efficiency, eliminate wireline intervention and coil tubing milling operations, the decision was made to test an openhole multistage fracture system (OH MSF). This came with the challenge of ensuring adequate reservoir contact, comparable to the cemented plug and perf operations, where 21 perforation clusters, in average, are targeted. The OH MSF technology chosen consists of multiple frac ports per stage with high pressure mechanical packers to isolate each stage and slip-on oil swell packers, to isolate the individual frac port within a stage. This new method of diversion within the compartment itself helps to ensure that small variances in pressure between nozzle ports are isolated preventing the fracture operation within a stage from consolidating to a single-entry point. Like standard ball drop sleeve systems, the OH multiple entry frac sleeve system uses progressively increasing diameter balls to open each stage. One single ball will open all the ports in one stage simulating multiple clusters per stage. This allows for an increase in reservoir contact when stimulating large openhole lengths. Case Study Well-A was completed with six multi-entry stages, three entry points per stage, and one toe stage utilizing a hydraulic port resulting in a total of seven stages and 19 frac sleeves. The isolation plan for this well consisted of mechanical packers between the main nine stages and slip-on constrictors between the individual ports within each stage. Each fracture port was engineered with three jets of 0.563 in. hole diameter as part of the limited entry design. All the fracture stages were performed as per design. The initial production response was better than offset wells completed with plug and perf technique. A production log suggests contribution from 75% of each individual jet, indicating the proper diversion was achieved. Using a seven-stage openhole system yielded to 17 effective fractures contributing to production. By utilizing OH Multiple Entry MSF system technology for limited entry fracturing, Saudi Aramco has improved reservoir productivity and operation efficiency. This is the first time an openhole multistage fracturing system combining mechanical and constrictor swell packers has been deployed to promote limited entry diversion. This qualified and field-tested novel completion methodology ensures proper fracturing diversion between frac-ports located within the same stage. The benefits of this technology include improved reservoir contact, operation efficiency, cost reduction and placement improvement.

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.