Geomechanical effects of oilfield chemicals on sand failure in reservoir rocks

Abstract

Sand failure may result in the production of formation sand at the same time the formation fluids are being produced. This work examines the effects of some commonly used oilfield chemicals, specifically, biocide, corrosion inhibitor and scale inhibitor, on the geomechanical strength of reservoir rocks such as limestone and sandstone. A combination of rock mechanical testing, grain size distribution analysis and analytical techniques are used to establish and define the effects of these chemicals on grain dissolution and unconstrained compressive strength. The results suggest that some interactions such as chemical reaction (dissolution/precipitation) between the oilfield chemicals and the two different types of reservoir formation rocks and transport of grains occurred following the exposure of the rocks to the oilfield chemicals leading to the weakening of the grain fabrics rocks and consequent reduction in unconfined compressive strength. The implications of the results for the strength reduction and sand production are discussed.

Evaluation of Interactions Between Oilfield Chemicals and Reservoir Rocks

“…This could be explained by the fact that the carbonates have less favorable mechanical properties due to low degree of lithification (Durmeková et al 2003). Wuyep et al (2018) found an 18, 44 and 55% reduction in the UCS of sandstone samples from Niger Delta, Nigeria, exposed to ATMP, betaine and glutaraldehyde. When limestone samples from the same country were exposed to these chemicals under static condition, a 29 and 41% reduction in UCS was recorded in betaine and glutaraldehyde.…”

“…The objective of these analyses was to identify and analyze any chemical changes that might have taken place within the rock fabric and the corresponding mechanical damage to the rock fabric. The SEM, EDX and XRPD analyses were carried out as described in Wuyep et al (2018).…”

“…Despite the efforts made by these authors to explore the interaction between the scale/corrosion inhibitors and the formation rocks, questions regarding the effects of the interaction between the scale inhibitor, corrosion inhibitor, biocide and the formation rock on the geomechanical strength of the rocks, and the mechanisms of interaction still remained unanswered. Wuyep et al (2018) conducted studies on the interaction of betaine, aminotri (methylene phosphonic acid)-ATMP and glutaraldehyde with sandstone and limestone to determine their effects on the geomechanical strength of these rocks. The study was done under static condition which is purely diffusion transport driven.…”

“…Dynamic saturation, which involves injection and flushing out of the chemicals (flow-back) at a determined flow rate, mimics production from the reservoir formation following chemical injection. Further, Wuyep et al (2018) did not consider the effect of the oilfield chemicals on the petrophysical properties of the rocks.…”

“…The current paper is an extension of the work of Wuyep et al (2018) and seeks to investigate the effects of scale inhibitor, biocide and corrosion inhibitor on the geomechanical strength of reservoir rocks under dynamic condition (convection and diffusion transport) and explore the geomechanical failure mechanisms arising from the interaction of these chemicals with reservoir rocks using an integrated approach.…”