April 17, 2017
Costs and Causes of Proppant Flowback
Part I of a Series on Flowback Economics
Proppant flowback is nothing new to operators of both vertical and horizontal wells. Proppant flowback reduces well profitability through both production downtime (missed revenue) and well clean up mitigation costs. At Fairmount Santrol, we’re devoting considerable time and attention to not only understanding the physical mechanics of flowback, but also to arriving at a better understanding of how well owners can achieve better short-term and longer-term well economics by addressing this problem at the right time in a well’s operating life.
Short-term and longer-term production losses are one dimension of the flowback problem. Proppant losses due to initial proppant flowback, as well as additional proppant losses that can continue for years afterward, lead to fracture width reduction that diminishes conductivity. Proppant flowback also can cover up or fill in perforations, limiting the fluid flow path to the wellbore, all leading to reduced production and lower Net Present Value (NPV) of the well.
Another downside of flowback that’s been receiving more attention in today’s economic climate in the oilfield is the cost of mitigation — especially for equipment-damaging flowback that occurs during completion and initial production.
What does proppant flowback cost?
When an operator encounters proppant flowback, remediation is expensive. Proppant can cause major damage to downhole equipment, such as an electrical submersible pump (ESP) and a bottomhole rod pump, in addition to surface equipment, such as the choke, pipelines, and storage facilities.
We carried out a Voice of the Customer survey with large operators in the Permian basin about their total proppant flowback mitigation costs during the first two years of well operation. The overall feedback was that for a horizontal well the average costs varied between $175,000 and $400,000, mostly depending on whether the Electric Submersible Pump (ESP) could be refurbished, or a brand-new ESP was needed. For a vertical well, the average proppant mitigation costs varied between $50,000 and $150,000. These large operators carried out well cleanup because it’s essential to remove unwanted proppant from the wellbore (proppant that has flowed back from the fracture and into wellbore) to reestablish production from perforated intervals.
Why does flowback happen?
Unfortunately, the industry does not have a clear understanding of when to expect proppant flowback because numerous factors can be involved, sometimes in combination. These can include:
- Bottomhole formation closure stress and closure-stress rate
- Flowback rate and shut-in time after completion
- Fracture width, height, and tortuosity
- Proppant mesh size and angularity
- Proppant distribution inside the fracture
- Curable proppant setting (curing) that forms a chemically bound three-dimensional network in the fracture.
Can proppant flowback be prevented?
Operators can optimize their hydraulic fracturing operations by applying one or more of the following solutions to the proppant flowback problem:
- Chopped fibers or thermoplastic strips
- Forced closure
- Mechanical screens
- Production rate reduction
- Surface modification agents
- Liquid resin
- Curable resin-coated proppant
Part two of our proppant flowback blog series will discuss these prevention tactics and provide some insight into where they work the best and how they compare with one another in improving production and maintenance economics.
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