Research status and progress of functional fracturing proppant used in oil and gas development (II)

5. Proppant for water treatment

Although hydraulic fracturing technology can increase production, it will cause groundwater pollution. The circulating water contains chemical substances used for hydraulic fracturing treatment, naturally produced concentrated brine, and a small amount of radioactive substances, such as Ra-226, Ra-228, Th-232, and U-238. In order to avoid environmental pollution, further treatment of circulating water is required. Researchers found that this problem can be solved by synthesizing water treatment proppant. This kind of proppant is harmless to the circulating water by compounding the radioactive material absorbent and hazardous chemical reagent absorbent.

6. Self suspension proppant

In order to quickly obtain artificial fractures in reservoir, high viscosity fluid is usually used as fracturing fluid during hydraulic fracturing operation. However, high viscosity fluid will lead to formation damage and irregular fracture geometry, resulting in a decline in production. Low viscosity fracturing fluid is conducive to obtaining artificial fractures with regular shape and will not cause formation damage. However, the low viscosity fracturing fluid makes the proppant settle too fast in the fracture, leading to the shortening of the artificial fracture length, or even partial fracture closure, thus reducing the production. The self suspension proppant can effectively avoid the problem of proppant settling in low viscosity fracturing fluid. The density of the self suspended proppant is lower than the viscosity fracturing fluid, so it can be suspended in water, avoiding the use of fracturing fluid. Self suspension proppant is usually obtained by coating low-density resin and hydrogel.

7. In-situ proppant

In situ proppant refers to the self generated proppant after physical and chemical changes in the reservoir. The synthesis principle is: when the external conditions change, such as temperature, pressure and pH value, the phase change reaction of the liquid phase is used, that is, the proppant with spherical shape can be spontaneously formed under the action of free energy in the process of liquid phase transformation into solid phase. The proppant manufactured by this method has the advantages of convenient use and simple construction.

8. Wood proppant

Wood proppant is a kind of ultra-low density proppant made from natural materials containing lignin, including walnut granules, jujube powder and fruit shells, through atmospheric drying, screening and film covering. The density of wooden proppant is usually less than 1g/cm ³， It can be suspended on the water (fracturing fluid) surface, which can increase the conductivity of fractures in oil and gas reservoirs, so as to achieve the purpose of oil and gas production increase.