Intrusion or embedment of formation sand and fines from unconsolidated formations into proppant packs is known to diminish effective propped- fracture width, thus impacting fracture conductivity and potential well productivity. The work presented in this study shows that it is necessary to control the invasion of formation particulates into the proppant pack in the fracture to maintain its conductivity, and ultimately, the productivity of the well.
Core face materials of unconsolidated sand were used in examining their impact on fracture conductivity under high gas flow rates and frequent stress cycling. Results of laboratory testing indicates that on-the-fly coating of proppant with surface-modification agents (SMA) can provide an effective means for treating the formation surface in the fracture. The transfer of SMA from the proppant to the formation sand allows the loose, unconsolidated material to be transformed to a cohesive, bounded porous medium. As a result, it was observed that in all proppant types used in this study, the amount of formation material that appeared to be filling pore spaces in the proppant pack was much greater for the uncoated proppants. The coated proppants showed much less formation intrusion and much less formation material filling the porosity in the proppant pack. The effects of non-dDarcy flow are also examined and compared to baseline data. The beta factor of the coated proppant is lower than that of the uncoated proppant under nearly all test conditions.
Formation fines are known to cause severe formation damage during production, limiting the potential production of the well. Many factors contribute to the migration or movement of formation fines. Various techniques have been developed in the industry through the years for examining fines-stabilizing solutions to overcome the effects of fines migration. Acidizing has been used to dissolve fines for "unblocking" and enlarging the pore throat in the formation near the wellbore to increase the permeability of the formation. Other chemical treatments, including (1) clay-stabilizing surfactants as part of the completion fluids, or (2) polymers in remedial operations, have been applied to minimize fines migration and enhance the well productivity. These treatments commonly require the treatment fluids to be injected deep into the formation matrix, allowing the surfaces of the fines and pores to be in contact and interact with the treatment fluid. Large volumes of treatment fluid are often required to achieve the desired results. Most such treatment fluids provide only temporary solutions, because they tend to desorb with time and with production of fluids from the well.