During hydraulic fracturing, a large amount of aqueous fluid is introduced into the formation (some cases > 500,000 bbls). This fluid becomes trapped within the fracture and formation, experiencing higher temperature (up to 150 ºC) and/or higher hardness and salinity (up to 300,000 ppm) with exposure to formation water and temperature. This process, which can include lengthy shut-ins, leads to formation damage through water blockage resulting in fracture conductivity impairment. This damage can be mitigated by the use of flowback aids which are stable to these conditions, enhancing fracture clean-up and thereby hydrocarbon production.
This study presents the development of novel formulations which are effective for fracture clean-up and production enhancement under harsh conditions. These flow improvers enhance the interfacial properties and relative permeability of crudes (collected from Eagle Ford, Permian, Bakken) up to 150 ºC and 300,000 ppm of total dissolved solids (TDS) over an extended period of time.
The stability to temperature and salinity of different flowback aid packages was evaluated in aging cells at 150 °C and 200 psi. The interfacial properties of flowback aids in brines with a range of TDS levels were examined at different temperature. The effect of the flowback aid treatment on the wettability of ground shale and proppant is also studied via imbibition and centrifuge drainage tests. Proppant regain permeability and modified fracture conductivity testing on split sandstone and shale cores with relatively low proppant loading (<1 lb/ft2) was conducted to evaluate the effectiveness of different flowback aid treatments. The results showed that the developed flowback aid packages have superior temperature and TDS tolerance compared to conventional surfactants. Relatively low performance loss due to surfactant adsorption on shale and proppant was achieved. The optimized flowback aids packages attained low interfacial tension values with Permian, Bakken crude oils, and Eagle Ford condensate over a wide range of temperature and TDS values. The high temperature and brine stability of the developed surfactant systems allow them to be used for fracturing or refracturing at high temperatures and with high TDS produced or flowback waters.
Novel/Additive: The result demonstrates that flowback aids with consistent interfacial property is critical in enhancing fracture conductivity, thereby improving hydrocarbon production.