Journey of a Technology from Lab to Readiness for Field Application: Enzymatic CaCO3 - A Novel, Environment-friendly System for Conformance and Sand Consolidation

Abstract

Long horizontal wells are hydraulically fractured or acid stimulated to economically develop chalk reservoirs in the North Sea. To separate the zones and ensure conformance, each fracture or zone is separated by isolation packers and flow is controlled with a sliding sleeve. With time, conformance control capability of the lower completion may be lost if the sliding sleeve is stuck open or holes are eroded or corroded in the lower tubing. If a shortcut has developed between an injector and producer, either during stimulation or operation of the well, the consequence of losing conformance capability of the lower completion is more severe. Another scenario with serious consequences occurs when the well has been hydraulically fractured with proppant and the proppant is back-produced without a possibility to close off the zone. To mechanically fix this conformance issue, it would require working over the well and replacing the lower completion. In an old (30-40 years) well, this is a challenge. A better solution is to solve the problem chemically by consolidating the sand in the fracture or plugging the fracture connecting the injector and producer. Recovery from the reservoir will then be optimized and the solution is likely to be cheaper than working over the well. Enzymatic CaCO3 technology is a novel chemical system that can be used for plugging fractures and consolidates sand in propped fractures in horizontal wells. All chemicals used offshore in the North Sea need to be compliant with OSPAR regulations; the Enzymatic CaCO3 system is classified as environment-friendly. It also has predictable chemistry and is completely reversible. This paper discusses the process of maturing the technology from concept to readiness for field implementation covering lab testing, IP protection, chemical procurement strategies, environmental impact evaluation, and quality assurance process during field application.

A Review of Enzyme-Induced Calcium Carbonate Precipitation Applicability in the Oil and Gas Industry

“…The enzyme-based CaCO 3 precipitation was found to be an effective means of consolidating proppant and plugging fractures in the induced propped fractures. Laboratory experiments were demonstrated to consolidate the sand pack, and plug fractures caused considerable permeability reduction because of enzyme-based calcium carbonate precipitation ( Bansal et al, 2014 ).…”