An average Costco store has over 3 football fields worth of floor space but only 4,000 different products for sale compared to 30,000 at typical grocery store. With over 100 million members, Costco makes it clear that the benefits of low prices through economies of scale can outweigh less flexibility in choice. E&P operators are making a similar tradeoff between cost and operational flexibility through the increasing adoption of simul-frac operations. While two wells can be completed at the same time by running two frac crews at once, most consider true simul-frac operations as having a single larger frac crew complete two wells simultaneously. As depicted below, this means a single crew can complete twice as many stages in a given period of time, cutting overall completion times roughly in half.

Source: Darcy Partners

While this simplified depiction demonstrates the potential speed advantages of simul-frac operations, in reality there are significant advantages and challenges for both zipper frac and simul-frac operations. The industry has improved zipper frac efficiencies primarily by pumping jobs faster through increased fluid rates and pumping fewer stages through limited entry designs that increase stage length. A wide range of quick connect systems (discussed at a Darcy Forum in February 2021), which speed and automate transition times between frac and wireline operations, have also improved operational efficiencies. These factors have enabled operators to become highly efficient in terms of pump hours per day, which Darcy member data shows is as high as 22 hours per day or more for 40% of operators on their best days.

Source: Darcy Partners

As outlined in a study recently published by Chevron titled, Simul-frac Journey in the Permian Basin, the push for higher rates to drive efficiencies in zipper fracture is likely hitting diminishing returns as higher rates lead to increased costs of friction reducer chemicals and higher equipment costs (e.g. 15,000 psi pressure control equipment). These diminishing returns have led to increased interest and use of simul-frac, however the technique is not without it's own set of challenges, which include:

• Increased equipment footprint
• Higher sand and water rates than zipper frac jobs
• Lower treating rate per well
• Decreased flexibility of frac design

Increased Equipment Footprint

To handle increased fluid rates compared to zipper fracs, simul-frac jobs typically require additional pumping equipment. This, as well as the need for a second wireline unit and crane increase overall equipment footprint, leading to the need for larger pad sizes. Larger pads may be cost prohibitive, not feasible due to geographic limitations, or impractical if a pad has already been permitted and constructed. While Chevron was able to use a simul-frac crew on their standard pad size, significant care in operations was required as limited space was available for coiled tubing equipment to be brought in if intervention was needed.

Higher Sand and Water Rates

Higher total water and proppant throughput requires careful logistics planning. Standard sand delivery systems may not be capable of keeping up with increased rates and booster systems may be needed to increase total rates.

Lower Treating Rate Per Well

With flow split between wells, even at at total pump rate of 140 barrels per minute (bbl/min), each well receives 70 bbl/min, which is on the lower end for many modern designs. Lower treatment rates lead to longer per stage pump times as well as shorter and therefore additional stages.

Decreased Design Flexibility

The use of a single blender means the same proppant schedule must be delivered to each wellbore. If an issue is encountered in one well, such as a screenout, a simul-frac job could require pumping on both wells to stop, mitigating the time savings of pumping two wells at once. While some have also raised concerns about increased operational complexity for pads with uneven numbers of wells, Chevron's work demonstrated several examples of successful simul-frac operations on pads with 5 and 7 wells using creative treatment schedules, such as the one depicted below for a 5 well pad.

Source: Darcy Partners

Despite these potential challenges, if executed properly, simul-frac operations can deliver significant cost savings. In the Chevron study, cost savings averaged 6% over a 6 pad trial, leading the authors indicate that simul-frac is currently the default technique for their Permian operations. While these results are highly encouraging, additional questions remain to be answered:

• How will the different completion designs used impact ultimate recovery of simul-frac pads?
• What changes to post-completions planning need to be made to optimize the time savings from simul-frac operations?
• Can well construction costs be lowered or lateral lengths extended if frac designs have lower treating rates?

The Darcy team looks forward to discussing these questions and seeing additional simul-frac case study data at our upcoming Simul-Frac Forum on August 25th where ProFrac will share lessons learned from the field.

Do you have a question about simul-frac operations? Let us know with a comment below!