Resource extraction and harvesting technologies are one of the patentECO Indexes, and they can include cleantech. These technologies provide the raw materials needed to support societies and they provide a fundamental basis for the economic engine fueled by a free-market economy. In this post, two recent cleantech patents in widely separated areas of resource extraction – hydraulic fracturing or “fracing” and commercial fish trawling – are described.
The patent cognoscenti often use the word "teach", to explain what an inventor's invention is. Our definition of "teach" is:
An inventor is granted an exclusive right to their invention in exchange for teaching others skilled in the art how to make their invention by way of the information in the patent. With respect to prior art, teach is defined as informing and instructing by way of the documents making up the prior art. The prior art references teach the technology disclosed in them or revealed by them.(For more patent-speak, see the Way Better Patents Glossary.)
Improving Hydraulic Fracturing Efficiency
Hydraulic fracturing (“fracing” or “fracking”) is a technique used to stimulate the production of gases and fluids from underground geologic formations. It is based on the high pressure injection of fluids into a gas or oil wellbore for the purpose of fracturing the geologic formation to increase its permeability, thus stimulating the flow of the desired products into the wellbore. Included in the injected fluid is a “proppant”, typically sand, that holds the fracture open and permeable after the fluid has dispersed. The increased formation permeability, and therefore product flow, will be a function of the total length of the propped fractures. Previous Inkling posts on fracing are here and here.
Patent US 8,127,850, "Method of treating subterranean formations using sequential proppant stages" seeks to increase the effective propped lengths by using ultra lightweight (ULW) proppants. The patent was issued to Harold Dean Brannon (Magnolia, TX) and six co-inventors on March 6, 2012, and was assigned to Baker Hughes Incorporated (Houston, TX).
In the Brannon et al. invention the ULW proppants are provided in two stages, the first being either more dense or of a different particle size than the second-stage proppant. The two-stage pumping of proppants into the formation fractures increases the effective propped length of the fractures, and thus increases the overall permeability (and yield) of the formation over a one-stage proppant fracing operation.
Brannon et al. teach the hydraulic fracturing process:
During hydraulic fracturing, a viscosified fracturing fluid is pumped at high pressures and at high rates into a wellbore to initiate and propagate a hydraulic fracture. Once the natural reservoir pressures are exceeded, the fluid induces a fracture in the formation and transports the proppant into the fracture. The fluid used to initiate and propagate the fracture is commonly known as the “pad”. The pad may contain a heavy density fine particulate, such as fine mesh sand, for fluid loss control, or larger grain sand to abrade perforations or near-wellbore tortuosity. Once the fracture is initiated, subsequent stages of viscosified fracturing fluid containing chemical agents such as breakers, and containing proppants are pumped into the created fracture. The fracture generally continues to grow during pumping and the proppant remains in the fracture in the form of a permeable “pack” that serves to “prop” the fracture open. Once the treatment is completed, the fracture closes onto the proppants which maintain the fracture open, providing a highly conductive pathway for hydrocarbons and/or other formation fluids to flow into the wellbore. The fracturing fluid ultimately “leaks off” into the surrounding formation. The treatment design generally requires the fracturing fluid to reach maximum viscosity as it enters the fracture which affects the fracture length and width.
Fracturing fluids, including those containing breakers, typically exhibit poor transport properties. High pumping rates are required in order to impart a sufficient velocity for placement of the proppant in the fracture. In such treatments, the proppant tends to settle, forming a 'proppant bank', as the linear slurry velocity falls as a function of the distance from the wellbore. This effect is further believed to result in reduced stimulation efficiency as the effective propped length is relatively short. In addition, much of the settled proppant is often below the productive interval.
The recovery of the fracturing fluid is accomplished by reducing the viscosity of the fluid to a low value such that it flows naturally from the formation under the influence of formation fluids and pressure. This viscosity reduction or conversion is referred to as “breaking”. Historically, the application of breaking fluids as fracturing fluids at elevated temperatures, i.e., above about 120–130 °F., has been a compromise between maintaining proppant transport and achieving the desired fracture conductivity, measured in terms of effective propped fracture length. Conventional oxidative breakers react rapidly at elevated temperatures, potentially leading to catastrophic loss of proppant transport. Encapsulated oxidative breakers have experienced limited utility at elevated temperatures due to a tendency to release prematurely or to have been rendered ineffective through payload self-degradation prior to release.
By increasing the permeability and yield of individual wells through the use of this newly-patented technology, more natural gas and oil will be available.
These are good outcomes from using different types of sand.