An example application of proposed method for planning best initial response to kicks taken during managed pressure drilling (MPD) will be discssed. The decision tree (Smith & Patel, 2011) was described as a proposed tool for selecting a preplanned initial response to a kick occurring during constant bottomhole pressure (CBHP) method of managed pressure drilling. The decision tree is based upon the research done by an industry supported research project evaluating well control methods for managed pressure drilling. The Research (Davoudi et al, 2010) concluded that shutting in the well, increase casing pressure until flow in equals flow out and using an adaptation of MPD pump shutdown schedule to detect and shut in a low rate kick were three most widely applicable initial responses to kicks during MPD.
The candidate well for MPD will be described with all important parameters used in decision tree. All necessary calculations for determining expected pressure values were performed. Reactions that maximize kick tolerance were evaluated along with verifying pressure limitations of the pressure control equipment. Evaluation of surface equipment will be performed based upon the pressures expected on surface because of the kick. For any expected well control event, circulating (increasing Pc until Flow in = Flow Out) as well as non-circulating (shut in & MPD shut down with schedule) reactions will be evaluated.
Managed Pressure Drilling has gained industry wide acceptance as a useful tool to address challenges encountered during conventional drilling operations in overbalanced condition. According to definition by International Association of Drilling Contractors (MMS, 2008) defines MPD as an "adaptive drilling process used to precisely control the annular pressure profile throughout the wellbore" MPD has many variants designed for various purposes. (Hannegan, 2009) CBHP method of MPD has been the focus for this study. According to definition of CBHP method of MPD (MMS, 2008), "MPD is intended to avoid continuous influx of formation fluids to the surface. Any flow incidental to the operation will be safely contained using an appropriate process".
Use of Rotating Control Device and automated choke manifold creates a closed loop drilling system that enables enhanced control over the wellbore. CBHP method uses combination of Hydrostatic Pressure of the mud column and annular frictional pressure PAF (Equivalent Circulating Density ECD). During connections, loss of ECD (due to no circulation) is compensated by applying surface back pressure (PC). Continuous Circulation System (CCS) can also be employed to maintain constant bottomhole pressure. Other equipment such as Back Pressure Pump, Coriolis meter, pressure while drilling (PWD) tools and advanced computer software control can contribute to create more sophisticated form of CBHP MPD.
Figure 1 shows decision tree (Smith & Patel, 2011) for responses involving increase in casing pressure. These responses involve continued circulation into the wellbore while reaction is applied to control the influx. Figure 2 shows decision tree for responses involving either MPD pump shut down with schedule or shutting in the well. Detailed discussion about the use of decision tree, description of various parameters and sample application has been done in IADC/SPE 143101 (Smith & Patel, 2011). Utilization of the decision tree to plan initial reaction to a well control event will be discussed. Advantages and limitation of any particular reaction will be discussed. Evaluation will done on the basis of impact on kick tolerance, better control over the wellbore and improvement in safety.