The current trends to re-evaluate the need for traditional clay control additives and the interest in increasing hydrocarbon production from secondary fracture networks are leading to the use of more appropriate fluid compositions. Additives historically used to dehydrate or exchange interlayer cations in water-reactive phyllosilicates introduce instability in the reservoir matrix and have been used in shale reservoirs without thorough assessments of potential formation damage. Framing the need for clay control in these reservoirs solely on the need to control water-reactive clays led naturally to the removal of clay control additives from fluids during the recent downturn. While justified from a cost perspective, these simplified fluids were introduced without assessments of the impact of near colloidal (10-40um diameter) fines generation. Completion experts who realize the formation damage risk of fines generation recognized these problems.
This paper updates the industry on an approach to proportion clay control and shale stabilization with fluid design better aligned to reservoir mineralogy and the stress introduced on the reservoir during hydraulic fracturing. The paper reports swelling clay control and near colloidal fines evaluations from four world class unconventional oil & gas reservoirs in North America. Reproducible fundamental trends in CST and near-colloidal fines generation data are correlated to clay control additive type and use of oxidative breaker. Additionally, this new test method has the potential to be easily and commercially viable for rapid field evaluation to assess formation damage due to fines generation.
Copyright, 2018. Society of Petroleum Engineers