Flowback
- Also known as
- flowback water, load recovery, frac flowback
Flowback is the fluid that returns to the surface from a well after hydraulic fracturing, before and during the start of production. It is largely the injected fracturing fluid, mixed increasingly with water from the formation.
What is flowback?
After a well has been hydraulically fractured, it is opened so that pressure is released and fluid can return up the wellbore. The fluid that comes back in this early period is called flowback. At first it is mostly the fracturing fluid that was pumped in, along with some proppant and debris from the operation. Over the following days and weeks, the returning water increasingly comes from the formation itself, and oil or gas production rises.
Flowback and produced water
The two are often discussed together, and the line between them is gradual:
| Flowback | Produced water | |
|---|---|---|
| When | Shortly after fracturing, during cleanup | Throughout the life of the well |
| Origin | Mainly injected fracturing fluid | Mainly water native to the formation |
| Composition | Resembles the fracturing fluid at first, becoming saltier over time | Typically salty brine, often high in total dissolved solids |
Both are handled as wastewater: treated and reused in later fracturing jobs, or disposed of, often by injection into a saltwater disposal well.
Load recovery
The share of the injected fracturing fluid that returns to the surface is called load recovery. In many shale wells, much of the injected fluid never returns: it stays in the rock around the fractures, held by capillary pressure or absorbed into the rock by imbibition.
Retained fluid is not always harmful, and interpretations of low load recovery differ between formations. But water held in the rock next to the fractures can block the flow of oil and gas, a condition called a water block, and reduce early production.
Why flowback matters
- Cleanup and early production. How quickly and completely the well cleans up influences initial production rates and the shape of the early decline curve.
- Water handling cost. Flowback volumes, and their salt and solids content, determine storage, trucking, treatment and disposal costs.
- Diagnostics. The volume and chemistry of flowback give engineers information about the fracture network and the formation.
Surfactants in the fracturing fluid are used to lower interfacial tension and alter rock wettability so that less fluid is trapped and oil and gas can flow into the fractures more easily.
Flowback at Locus
Locus describes its SUSTAIN frac surfactant as improving flowback and cleanup after hydraulic fracturing by reducing interfacial tension and capillary pressure.
Frequently asked questions
Flowback is the fluid returning soon after fracturing and is mostly injected fracturing fluid. Produced water is water that comes from the formation and is produced throughout the life of the well. Over the first weeks, flowback gradually transitions into produced water.
Much of it is held in the rock around the fractures by capillary forces or absorbed into the rock’s pores. In tight formations, where pores are extremely small, those forces are strong.
It is collected at the surface and either treated and reused in later fracturing operations or disposed of, typically by injection into a permitted disposal well.
Sources
- flowback, SLB Energy Glossary
- Hydraulic fracturing water cycle, U.S. Environmental Protection Agency
- Produced water resources, U.S. Geological Survey