【本周专题：压裂增产】创新压裂：压裂砂&支撑剂新进展

Still struggling to understand how much proppant is enough to optimally deplete or drain a reservoir, the oil and gas industry now must focus on the long-term productivity of unconventional wells, Terry Palisch, Global Engineering Director for CARBO, said. With cost-cutting still king in this environment, the company saw a massive shift among its customers toward sand-based products. However, this shift raises questions around the sustainability and logistics of putting 20 million to 30 million pounds of sand in a well. For example, there are challenges around the shortage of sufficient-quality sand in some areas and the use of chemicals used in frac treatment. The disposal of flowback water also poses challenges, as do the number of trains and trucks required to transport sand to worksites.

By substituting sand volume with a low-density ceramic proppant, CARBOAIR, the company believes that operators can transport proppants further in the wellbore with 25% to 30% less water than typically used, reducing a fracking operation’s environmental footprint. The release of the new proppant began last year with two initial field trials; it has also been deployed in another field trial earlier this year, Mr Palisch said. CARBOAIR is an ultra-low density ceramic proppant with chemically engineered internal porosity and 2.0 specific gravity that offers 30% to 40% slower settling rates compared with sand. According to CARBO, the technology reduces the amount of proppant needed to keep fractures open versus conventional proppant, reducing water consumption and flowback treatment costs.

In early 2017 in Eddy County, New Mexico, an operator was able to stimulate a wildcat well with thin gross pay in the second Bone Springs formation by pumping in the low-density proppant as a tail-in to promote greater propped frac half-length. A total of 26 frac stages were pumped using a smaller amount by weight of CARBOAIR – 2.5 million to 3 million lb total, or around 100,000 lb per stage – to achieve the equivalent volume as 40/70 conventional sand. As a result, the well experienced a shallower production decline than other nearby wells, according to the CARBO study.

In another case study, an Eagle Ford operator had planned to drill two parallel offset horizontal wells. In one well, 20% of the final proppant in each stage – 100 mesh and 40/70 sand – was replaced with 40/70 mesh CARBOAIR. As a result, a 20% productivity increase was seen in the well, according to the company.

To help oil and gas companies understand where proppants are flowing in the subsurface, CARBO has been working to develop proppants that do more than just prop open the fracture. It plans to commercialize in the second half of 2018 its new product, QUANTUM, which allows an operator to detect proppants in the subsurface from hundreds of feet away.

Technology currently available for detecting proppants can see specialty proppant that contains either radioactive or non-radioactive-based tracers using gamma ray or neutron logs run in the wellbore. However, such technology can only detect the proppant location within 18 to 24 in. of the wellbore. It is measured using a log run in the wellbore, and this can be done basically at any depth reservoir, Mr Palisch explained.

The QUANTUM technology is meant to see electrically conductive proppant – or standard proppant with a metal coating – from hundreds of feet away from the wellbore. “To date, the proppant has been at depths up to 10,000 ft, although we do not know what the limit will be. It is measured using sensors located on the surface around the wellhead and pad,” Mr Palisch said.

Using electromagnetic methods, surface electric and magnetic field sensors and a specially formulated proppant, the technology has been tested in field trials in West Texas, the Marcellus and STACK plays. CARBO is currently holding its fifth and hopefully last field trial of the product, Mr Palisch said.

Tackling produced water

Proppant provider Fairmount Santrol sees the need for fracking technologies that not only boost production and require a lower upfront investment but are simpler to deploy and more environmentally friendly.

Sid Banerjee, Product Manager for Self-Suspending Sand at Fairmount Santrol, said he is excited about applying the company’s self-suspending sand production line, Propel SSP, to reduce the use of fresh water in fracking operations. Propel SSP 350 can tolerate water with up to 350,000 parts per million total dissolved solids. The product had a soft launch in January 2017; the company continues to revise the technology for various applications, including refractures.

“Water has been one of the biggest waste streams in hydraulic fracturing in North America, as water types used had to be relatively clean. This put the oil and gas industry in competition with farms, ranches, cities and other entities that consume fresh water. Water shortages in some areas have heightened concerns over available supply,” Mr Banerjee said.

In terms of future technology development, Fairmount Santrol is looking at well refracture technology as E&P firms seek to boost production at the lowest cost possible. For the tenth of the cost of drilling a new well, production can be boosted or regenerated from an underperforming well or old well. Refracking an old well could pay off if the well’s problem is solved. But companies short on time have often opted to drill a new well in a new area with a design they can understand, rather than reengineer an old one. “There’s considerable interest in the space, but not a lot of understanding about what makes a well a good refracture candidate,” Mr Banerjee said.