Addressing wellbore integrity and thief zone permeability using microbially-induced calcium carbonate precipitation (MICP): A field demonstration

Abstract

Microbially-induced calcium carbonate precipitation (MICP) is an emerging biotechnology for wellbore integrity applications including sealing defects in wellbore cement and modifying the permeability of rock formations. The goal of this field demonstration was to characterize a failed waterflood injection well and provide proof of principle that MICP can reduce permeability in the presence of oil using conventional oilfield fluid delivery methods. We compared well logs performed at the time the well was drilled with ultrasonic logs, sonic cement evaluation, and temperature logs conducted after the well failed. Analysis of these logs suggested that, rather than entering the target waterflood formation, injectate was traveling through defects in the well cement to a higher permeability sandstone layer above the target formation. Sporosarcina pasteurii cultures and urea-calcium media were delivered 2290 ft (698 m) below ground surface using a 3.75 gal (14.2 L) slickline dump bailer to promote mineralization in the undesired flow paths. By Day 6 and after 25 inoculum and 49 calcium media injections, the injectivity [gpm/psi] had decreased by approximately 70%. This demonstration shows that 1) common well logs can be used to identify scenarios where MICP can be employed to reduce system permeability, remediate leakage pathways, and improve waterflood efficiency, and 2) MICP can occur in the presence of hydrocarbons.