Controlled Pressure Drilling (CPD) Candidate Screening Methodology

Abstract

Controlled pressure drilling (CPD) has become the most effective drilling method to improve technical limit drilling time and reduce previously recorded lost time on offset conventionally drilled wells—when it is applied to correctly selected candidates. In addition, specific drilling techniques offered within CPD technology not only improve the time it takes to reach total depth (TD), but also have been proven to optimize reservoir section productivity and maximize economically recoverable reserves. CPD comprises three main techniques: air drilling, underbalanced drilling, and managed pressure drilling. This paper discusses the latest CPD techniques and the non-productive time that it can address. A methodology to properly screen all CPD techniques to reduce failure/misapplication and align objectives with expectations had been absent. This paper addresses the latest enhancements in an expert system developed to better understand and screen options for CPD operations. The Internet-based selection tool provides guidance by using key indicator questions, beginning with the primary objective(s) for the given wellbore section. If the specific CPD technique is known, the user can activate the online screening tool. The online screening tool considers a range of economic and technical parameters, as applied to algorithms and logic rules, to provide a relative ranking for each candidate of the CPD technique. Sensitivity analysis can also be performed to determine the impact of key uncertain parameters. Additional expert screening and selection methods are available upon the completion of the online CPD candidate selection process. The paper provides an overview of the Internet-based tool and methodology, in addition to supporting case histories. Introduction CPD is an adaptive drilling process that enables a more precise control of wellbore pressures through the use of engineered equipment and processes. The drilling process is becoming an important tool for drilling aging fields with depleted reservoirs, narrow pressure windows, and/or drilling issues. Drilling improvements stem from mitigating common drilling hazards that are caused by lost circulation, kick/loss scenarios, sour-gas influx, or simply slow drilling through hard formations; the end result is a reduction of avoidable cost. Loss of production and ultimate recovery result in an increase of the total cost per equivalent barrel of oil, reducing net present value (NPV). CPD effectively mitigates these issues, reducing non-productive time (NPT), improving productivity, as well as NPV, on both a well-to-well and field-to-field basis. The drilling process is defined by three major techniques:Air drilling (AD): Improve drilling economics by increasing rate of penetration (ROP) and extending bit life. Primarily applied in nonliquid hydrocarbon formations and the intent is to invite surface flow.Managed pressure drilling (MPD): Optimize drilling process by decreasing NPT and mitigating drilling hazards. The intent is not to invite surface flow.Underbalanced drilling (UBD): Increase reservoir productivity and maximize NPV by reducing formation damage and enhancing reservoir characterization. The intent is to invite surface flow. Fig. 1 provides more background on the individual techniques.