The number of widely publicized oil and gas well failures is a reminder of the engineering challenges associated with drilling activities and the importance of safety controls in well operation. These accidents highlight an area of significant engineering and liability concern in a burgeoning industry that is expanding into new geographic locations with local populations and regulators that are unfamiliar with extraction activities. They are also a reminder of the considerable engineering challenges producers face in the extraction of buried fossil fuel deposits under temperatures and pressures that require substantial engineering design and careful attention to material selection.
Advances in drilling technologies developed by industry are responsible for expanding the types of oil- and gas-containing formations that can be produced (e.g., Marcellus Shale, Utica Shale). Extraction of the payload involves drilling through complicated geological formations that requires reinforcement of the well to avoid leakage to the surface or surrounding formations. The cementitious well barrier must adequately bond to the steel well casing and the surrounding formation and maintain structural integrity throughout well exploration, production, and after abandonment.
Grout mix design is not a trivial engineering task, and many new admixtures have been developed precisely for these applications. Yet, according to a “pilot well integrity survey” published in 2010 in the Society of Petroleum Engineers (SPE) Production & Operations Journal, 18% of the wells in the survey had integrity failure, issues or uncertainties. The survey, conducted by the Petroleum Safety Authority Norway (PSA), concluded that there needed to be “more focus on barrier philosophy to avoid major incidents caused by unintentional leaks and well-control situations.”
Improvements in well barrier materials are now possible as are applications of sensing and concrete remaining life assessment technologies developed in other industries. In the spirit of proactive stewardship, real-time knowledge of well-integrity status combined with the ability to reliably assess well barrier remaining life will simultaneously protect company assets and assure public safety with industry’s ability to predict and prevent leak incidents.
The Importance of Allowing Sound Science to Guide Regulation
Some new frontiers of oil and gas exploration have become uncomfortably close to locales unfamiliar with drilling practices, benefits and potential hazards. The long history of industry is one of great success, but it is not spotless; even one spill or leak can be disastrous for the affected community. Fear of the possibility of similar events is the political impetus behind moratoria in multiple states. Such fears can be assuaged and industry practices improved through the application of modern technology and tools as described, and which will provide the assurance needed for confidence in industry’s ability to control well barrier integrity.
Navigating the economic and political landscape is a challenge facing industry and government alike. With the promise of a new source of energy comes the enticing prospect of business profits, new jobs, and increased tax revenue streams. The central importance of structural well integrity starts at the exploratory drilling phase and continues through the well’s abandonment. In today’s economy, wells are continually being evaluated by industry for their production contribution and to ensure compliance with regulatory oversight. Remote sensing technologies used in other industries can be transferred and re-purposed to break through some of the operational and safety obstacles with the assurance that real time information provides, guiding the development of regulations yet to be written, and increasing confidence in well barrier integrity to protect business revenue and limiting potential liability by reducing the risk of leakage.
Proactive options include scientifically-validated, industry-accepted software that determines the expected and remaining life of placed concrete as a function of its operating environment. One example is STADIUM®, a program which models the migration of critical chemical species that cause corrosion and other failure processes. By using modeling technologies along with well-established analytical methods, oil and gas producers will obtain the information they need to evaluate the mix designs of existing grout systems, to conduct failure analysis, and to determine future performance and expected remaining service life.
Remote sensing technologies like Borehole Sonic (BHS) wireline logging tools are in development to improve the evaluation of grout bond and concrete grout quality by measuring full-field acoustic waves induced and propagated from inside the cemented steel casings of new and existing oil and gas wells. Such a wireline tool can be used to determine grout bond conditions at the casing/grout and grout/formation interfaces as well as the quality and strength of the grout and earth rock formation. Innovative approaches to sensor deployment during well barrier placement opens a wide variety of possibilities, including chemical sensors that when combined with the STADIUM® software could provide real time assessment of remaining barrier life during production and long after well abandonment.