Aqueous imbibition further investigation on contact area penetration enhancement for hydrocarbon extraction from tight rocks

Abstract

The rapid decline of production and low oil recovery in shale and other tight formations have been identified in practice. Surfactant EOR has been considered as one of the best options for those challenging formations. Many studies indicated that the oil recovery was improved by surfactant spontaneous imbibition in a huff-n-puff mode. However, the slow oil extraction rate and the limited penetrating area into the rock matrix by laboratory experimental results indicated it might be impractical for real-time extraction. To address this problem for the carbonate-rich tight formations, a new approach of forced surfactant imbibition process coupled with enhanced contact area stimulation (acidizing, for instance) was proposed. In this paper, samples from the Middle Bakken were used for the laboratory studies. A chemical formulation (CF) consists of surfactant, organic acid, and other components was designed to evaluate the effects on carbonate-rich rocks, rock microstructure and petrophysical properties (porosity and permeability). Oil recovery was also examined by forced imbibition with chemical formulation. Research results demonstrated that CF treatment could dissolve the carbonate minerals in the Bakken rocks resulted in the microstructure changes. These changes led to the injected fluid deeply imbibe into the rock matrix and therefore enlarge the rock-fluid contact area. Rock porosity and permeability were increased and oil recovery was significantly improved with the designed chemical formulation through forced imbibition. In a summary, this laboratory study of combination of acid stimulation and forced surfactant imbibition process may serve as a possible approach for a field application to improve the hydrocarbon recovery from well to well besides of huff-n-puff method.