Ways To Break More Rock When Hydraulic Fracturing
Around the top of the list of ways to make hydraulic fracturing more efficient is by expanding the area that is effectively fractured.
The need has been widely recognized because of a growing body of studies, many presented at the SPE Hydraulic Fracturing Technology Conference, which has also been a key forum for competing ideas on how to do better.
At this year’s gathering from 24–26 January, those doing completions are feeling the pressure to find ways to get more out of fracturing to help offset the cost of rising prices for services.
Productivity was a concern for organizers of a technical session Fracture Placement and Diversion, where the papers are aimed at cost-effective ways to use hydraulic force to create more productive openings.
There is growing evidence of the need for methods that are cost-effective, reliable, and repeatable in wells that vary widely.
“We have learned from fiber-optics and production logs that not all perforations are getting fractured. Before, we assumed they were because there was no way to determine whether they were or were not,” said Steve Mathis, a co-chair for the session who is a consultant and completion engineer for Chevron ETC.
And the goal now is to find ways to lower the cost per barrel enough to profitably produce from difficult rock for USD 50/bbl or less. The emphasis needs to be on producing more early and reducing declines over time, because the price of pumping a job is not likely to go down at a time when service companies are raising rates for pumping jobs where the pace is set by the volume of fluid pumped and the diameter of the casing.
The session offers some ideas for engineers needing to find better methods.
- A perforating gun (SPE 184883) designed to fracture a reservoir faster and more effectively by aiming a limited number of shots in the direction of the least stress.
- Getting more by hitting fewer spots along the wellbore. By using a new approach to limited-entry fracturing in Canada, Shell (SPE 184834) said it stimulated 33% more clusters compared to its previous limited-entry design.
- Two papers (SPE 188824 and SPE 184840) from Saudi Aramco covered how biodegradable particles from Halliburton were used to plug some perforations taking in most of the water and divert the high-pressure flow to perforations that otherwise would not be stimulated.
All offer the possibility of better performance, with the caveat that engineering is required. For example, Saudi Aramco’s papers elaborate on how it used its deep database about the rock and the performance of nearby wells to guide completion designs, resulting in the a higher total production of gas.
“You are not always going to get an increase with diversion. You need to engineer it,” said Francisco Fragachan, a co-chair for the session who is the director of marketing and sales for pressure pumping services at Weatherford and a strong advocate for diverters.
Weatherford and other big service companies are pushing diversion using their own approaches to create both more fractures and more even stimulation. They want to get past the notion that diversion is best used to refracture wells when there is no affordable way to use the hardware normally used to isolate stages during fracturing.
An example is offered by a paper from ConocoPhillips about how it used diversion, among other tools from Schlumberger, to fracture an underperforming well on the North Slope of Alaska.
Selling diversion as a routine part of new well completions will require lower-cost material—Fragachan said Weatherford can now produce its diverter for a fraction of what it cost a couple years ago. It can reduce the number of diverters needed per job by using a data-driven design to limit the risk that more diverters than planned will be required to temporarily seal dominant perforations.
The session is not offering any quick fixes to more effective fracturing. For example, the opening paper (SPE 184839) comparing two widely used fracturing methods—plug and perforation where multiple clusters of perforations are stimulated within stages isolated by packers, and pinpoint fracturing using coiled tubing to target more hydraulic force on a smaller target—shows each has its plusses and minuses.
“The keynote Chevron paper compared the pinpoint vs. plug and perf, and it is just not clear if one is better than the other,” Mathis said, adding that asset teams need to decide based on the project’s criteria for success.
Some fracturing methods allow more time to consider options, but there is a limit.
“Taking time to decide where you are going to perforate is all fine and good, but the economics do not allow you to do one every 6 months,” he said, adding the industry is still “talking about going faster and faster, and reducing operating costs.”
Ways To Break More Rock When Hydraulic Fracturing
Stephen Rassenfoss, JPT Emerging Technology Senior Editor
12 January 2017
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