Core restoration: A guide for improved wettability assessments

Abstract

The initial wetting of a reservoir sets a limit for the EOR potential during water-based recovery operations and “Smart Water” injection. For this reason, an improved understanding of the factors influencing the wetting can help to control and better forecast oil production during water-based floods. To preserve and reproduce the original reservoir wettability is a challenging task and wrong cleaning and core restoration procedures can lead to incorrect wettability estimations and thus induce serious errors when evaluating the initial wettability of a reservoir system or its EOR potential by water-based methods. Thereby, there is a need to improve the chemical knowledge on interactions among the rock, brine and fluids present in reservoir systems. This will help to understanding the influence of the parameters affecting wettability during cleaning and core restoration processes. Understanding which are the main parameters influencing oil recovery processes is of great relevance. The objective of this document is to provide suggestions for added-value experiments, complementing and challenging the standard RCA and SCAL procedures, prior to performing experimental research in which wettability and wettability alteration processes are important. Lessons learned will be highlighted and new ideas to optimize core restoration protocols to preserve and closely reproduce wettability are put forward. These recommended practices target core restoration procedures after the core material has been received in the laboratory. The target audience for this document is engineers and scientists with an interest in core preparation for wettability studies.

Evaluation of Surface-Active Ionic Liquids in Smart Water for Enhanced Oil Recovery in Carbonate Rocks

“…After equilibrating the S wi established by the desiccator, reproducible initial oil saturation and initial core wettability were established by introducing a controlled, equal amount of crude oil into each core. 65 Using a Hassler core holder in horizontal position at a confining pressure of 20 bar, each core was first vacuum-saturated with 1 PV of Res40-m oil and then flooded with 4 PV Res40-m oil at 0.2 cm 3 /min (injecting 2 PV in each direction). The whole process was performed at 50 °C.…”