The North American oil and gas industry continues to focus on smaller pore space and there is a continued need to protect and enhance the pore space and fracture networks in our reservoirs. To achieve this, our team has developed and tested a new category of bio-based embedment control fluid additives, that has shown to directly improve reservoir performance after flowback by slowing the reduction of fracture conductivity in hydraulically fractured rock.
Unconventional reservoirs are mineralogically complex. There is an array of minerals that are sensitive to invading waters including 2:1 layer silicates; "clays", oxides, substituted carbonates and freshly fractured silicates like quartz and feldspars. In North America, the clay fraction of the major plays is largely barren of discrete smectite, thus common clay control additives or the use of produced water brines for this purpose is poorly justified, and in fact promotes sloughing of the finest fractions from the fracture face (Landis et. al, 2018). In addition to fracture face softening, fines generation is a pronounced risk factor in reservoir damage mechanism especially with the use of common clay control additives.
To address this problem in our industry, the team functionalized bio-based polymers to maximize polydentate encapsulation of fluid sensitive minerals on the fracture face. This interaction is exploited to reduce reservoir damage in the crucial early stages of the stimulation process.
Molecular design, regain permeability testing and, finally, controlled field applications of the embedment control additive are shown in this paper to provide new realized value in the first year of production and beyond. The new bio-based additive differs from other higher molecular weight polymers used in the stimulation process. Smaller linear molecules functionalized with inhibitive substituents that do not exchange with the cations or anions in the mineral structures. When compared the larger polymers used for friction reduction, the targeted approach for the most interactive sites along the fracture face are addressed preferentially.
A more direct indicator of embedment control is obtained with regain permeability analyses. Assessment of the new bio-based product was conducted on Wolfcamp landing zone facies, and the Eagle Ford formation targets. All tests were run at representative confining pressures and temperatures, and against KCl baselines. A case study was performed in the field and highlighted the product's capability with both a reduction in turbidity during flowback by 350%, and production enhancement of the wells performance indicating the potential of increased performance with proper reservoir protection. In summary, this paper highlights the need for reservoir protection, a novel approach to minimize formation damage, and both laboratory and field testing of the process to prove the performance enhancement of minimizing formation damage.
