Minimize Formation Damage in Water-Sensitive Unconventional Reservoirs by Using Energized Fracturing Fluid

Abstract

Slickwater has been widely used for hydraulic fracturing as it is inexpensive and able to carry proppants into the fracture. However, such fluid is unsuitable for water-sensitive formations, such as Montney. Water saturation around the fracture increases and clay swells when water leaks-off into matrix, both hindering natural gas flowing from matrix into fractures. N 2 or CO 2 energized water-based fracturing fluids have been widely used in water-sensitive formation as they can minimize fluid leak off during fracturing and achieve higher load fluid recovery during flow back.In this paper, multi-phase numerical simulations are applied to study the formation damage mitigation in Montney tight reservoir by using energized fracturing fluid. A simulation model is built and history matched with flow back and early production data of a typical Montney tight gas well. The behavior of multi-phase fluid leak off and flow back is studied, and the sensitivity of foam quality of fracturing fluid on load fluid recovery and well after stimulation productivity is analyzed. Statistical analysis is conducted on the stimulation and production data of over 5000 Montney wells to study the performance of energized fracturing in water-sensitive Montney formation. It is found that multi-phase fracturing fluid has less dynamic fluid leak off than that of a single phase fracturing fluid (i.e., water), and the major fluid leak off occurs during the static leak off period between the end of the stimulation processes and start of the flow back. Gas phase penetrates deeper and faster into the reservoir matrix in comparison with the liquid phase, which greatly contributes to flow back of fracturing fluid. Formation damage caused by fracturing fluid leak off can affect both early and long term production. In addition, N 2 -foam leads to the highest load fluid recovery in Montney formation, which is 1.6 times of that of CO 2 -foam. This work provides critical insights into understanding the performance of using energized fracturing fluid to mitigate formation damage in tight formations.

CO2 Foam as an Improved Fracturing Fluid System for Unconventional Reservoir

“…In water-sensitive reservoirs possessing high clay contents, fracturing fluid containing a small amount of water and large gas volume is preferred in order to reduce formation damage caused by high capillary pressure and permeability discontinuity as the impacts of clay swelling [25]. Foam also can reduce the damage around wellbore due to invaded fluid which eventually reduces the water volume used for hydraulic fracturing.…”

Development and Evaluation of an Acidic Shear-Tolerant Nanosheet-Enhanced Cross-Linked Gel System for Hydrofracturing

“…The success of this operation depends on whether the fracturing fluid has satisfactory rheological properties and a suitable proppant carrying capacity . Many novel fracturing fluids, such as viscoelastic surfactants (VESs), slick water, supramolecular polymers, energized fluids, and supercritical carbon dioxide (CO 2 ), have been designed and developed through oilfield chemistry research. − Nevertheless, traditional guar-based linear or cross-linked fracturing fluids are still the most commonly used fluids in oilfields due to their desirable performances and low costs. − …”

Synergistic Effect of Sodium p-Perfluorononenyloxybenzenesulfonate and Alkanolamide Compounding System Used as Cleanup Additive in Hydraulic Fracturing

“…Water-based fracturing fluid is the most commonly used fluid, such as guar gum fracturing fluid, slick-water fracturing fluid, clean fracturing fluid, and so on. , However, it is reported that usually only 5–50% of the injected fluid can be successfully returned to the ground. These retained fluids (or so-called filtration loss fluid, or invading fluid) often cause greater damage to the reservoir matrix permeability, such as water-sensitivity damage and water-locking damage. − Water-sensitivity damage can be improved by adding clay stabilizer into the fracturing fluid, while well shut-ins after hydraulic fracturing and adding cleanup additives are effective for water-locking damage. − The effectiveness of well shut-ins after fracturing depends on the reservoir physical properties. It has been also pointed out that well shut-ins may reduce the fracture/matrix connectivity, adversely affecting overall hydrocarbon production.…”