Managed Pressure Drilling (MPD) offers the capability to control an influx dynamically, without conventionally shutting-in. Some current methods use applied-back-pressure (ABP) to force flow exiting the annulus to equal flow entering the drillpipe, which is interpreted as influx cessation. However, solely ensuring flow continuity does not imply influx cessation, unless the annular fluids are incompressible. In this work, the impact of compressibility on dynamic well control is investigated. The transient response of compressible, multiphase flow in the annulus is examined using mass conservation over a control volume.Limitations of Q out = Q in indicating influx cessation are explored, and an improved ABP dynamic well control technique is proposed. The new technique is applicable in MPD operations where conditions warrant dynamic well control rather than conventionally shutting-in.It is shown that with some current methods, influx may not cease once flow out is constrained to equal flow in. It is also shown that in some situations, influx ceases before flow continuity is achieved, resulting in excessive bottomhole pressure. These outcomes are consequences of in-situ gas compressibility, making it invalid to solely rely on Q out = Q in to indicate influx cessation. The proposed technique is shown to offer accurate determination of influx cessation, even when compressibility is significant. New pressure and pressure derivative based parameters that carry the signature of influx cessation are defined. It is shown that consideration of these parameters appreciably increases the likelihood of successful well control. Several examples are shown to illustrate the new approach with the use of the new signature parameters.Numerous transient, multiphase flow simulations have supported the key analytical conclusions from this work.The results of this work are expected to improve the reliability of dynamic well control using ABP during Managed Pressure Drilling operations. Further, the new signature parameters are easy to monitor and interpret, and together with flow rate provide valuable additional information to assist dynamic well control.

The MPD Operations Matrix was introduced in 2007 to serve as an operational guide for drilling MPD sections. The intent of the matrix is to balance operational, well, and equipment limitations with 'acceptable' influx volumes. The operations matrix has become the cornerstone of MPD projects worldwide, and is in fact a mandatory component of planned MPD wells in the Gulf of Mexico. In its current format, guideline for use of the matrix include developing criteria to categorize an influx such as its state, rate, duration, and size. Calculating these criteria and populating the matrix with them all can lead to some confusion, and many default to including only an influx size for simplicity, despite the fact that the other criteria can help in characterizing an influx further. Further, the acceptable influx size is most often limited to the detection capability of the MPD equipment, and not what the overall primary barrier envelope can handle.In this paper, a method for calculating acceptable influx volumes is outlined, and the calculation algorithm is adapted to a software tool. The results are displayed graphically in an Influx Management Envelope. The Influx Management Envelope is an evolution of the tabular MPD Operations Matrix, and includes all of the same influx indicator and pressure criteria, but offers a simpler, straightforward operational interpretation of influx limits.The effects of section depth, well geometry and hole size on influx volume limits will also be investigated, and development of a sample Influx Management Envelope is presented.

Managed Pressures Drilling (MPD) offers the capability to detect very small influxes when compared to using conventional rig equipment. Furthermore, the potential exists to control and circulate out the influx with the MPD equipment, without shutting in and performing conventional well control. When executed appropriately, this approach to managing an influx represents a higher degree of safety and enormous cost savings. However, managing an influx with MPD, particularly when a subsea BOP is in place, is quite different to conventional well control. A critical part of implementing MPD is to ensure that there is a clearly defined procedure for determining when MPD influx management must cease, and well control be initiated. A typical approach, regulated in some regions and voluntarily followed in others, is to create an MPD Operations Matrix before the operation begins, which outlines procedures that should be followed based on identifiable parameters following an influx. This matrix clearly identifies when it is appropriate to carry on with normal MPD operations, perform specific MPD influx control strategies, or shift to conventional well control. Forming the MPD Operations Matrix, however, can be challenging and has frequently been created inappropriately for the situations in which its use is intended. Development of a good understanding of how the well pressures and flow rates behave during MPD influx management is critical to ensuring a seamless handover between MPD influx management and Well Control. In this work, extensive transient multiphase simulation is used to demonstrate the sensitivity of surface pressures to well, drilling and influx characteristics and their resulting importance in the development of an operations protocol. Particular attention is given to influx volume, intensity and dispersion within a water based drilling fluid. Also considered are multiple wellbore geometries with primary focus on deepwater applications, oil based drilling fluid, pump rate and drilling fluid density and rheology. Where possible, findings are validated using recorded field data. This paper discusses and defines the transition between MPD influx management and conventional well control. The key parameters for calculating the boundaries of MPD influx management are determined and a protocol developed for smooth handover to well control operations. The protocol enables guidance to varying levels of influx management ranging from full influx detection and removal using the MPD equipment, to assisted shut in.

In high pressure high temperature (HPHT) reservoirs and exploratory wells, especially in deep water, there is a higher degree of uncertainty, which can increase the operational costs due to non-productive time (NPT) and operational problems due to the unpredictable nature of these wells. For these challenging wells with narrow windows, Managed Pressure Drilling (MPD) techniques offer cost-effective tools to increase the odds for achieving well and cost objectives assurance. There are significant benefits from early implementation of MPD in the project life cycle. These benefits include from improving operational efficiency to risk mitigation and safety enhancement. However, there is an enormous potential that many operators have been missing. This is related to the incorporation of MPD as a driver in optimizing the well design, which could greatly increase the possibilities of reaching target depth, and potentially prepare to eliminate one or more casing strings. Current well design process hinges on the ability to manage uncertainties by company or regulatory requirements, such as kick tolerance and safety factors. This work addresses the value added from implementing MPD in early stages in the project life cycle through the analysis of case studies. The cost savings from the impact on the well design are also discussed. This work also presents a in depth discussion on the benefits, and enablers of this approach. Furthermore, it presents considerations by taking advantage of dynamic processes facilitated with MPD. Finally, new guiding criteria to aim to constitute a systematic and integrated approach to ensure well integrity and optimize well design while also considering the operational implications and integral cost benefits is proposed to the industry. This paper represents the initial phase of a compressive long-term project to integrate two main components of well design. These are MPD adaptive well design, and statistical analysis based on variations of load and/or strength.

The Influx Management Envelope (IME) proposed by Culen et al. (2016) is an advanced, innovative way to assess influx conditions in Managed Pressure Drilling operations, offering an improved tool for the decision making process. This work presents the process of developing the IME concept on a real deepwater MPD operation for the first time. Limiting factors such as: shoe integrity, maximum surface pressures, and mud gas separator (MGS) flow rates (gas and liquid) have been taken into consideration in the process of developing a set of Influx Management Envelopes for three different hole sections. Two methods were used for developing the IMEs: Single bubble approach, as described by Culen et al.; and hydraulic modeling using a commercial transient, multiphase flow simulation software package. A comparison of the results from the single bubble calculation versus simulation methods is presented, highlighting the impact of gas dissolution and dispersion on the manageable influx volumes in MPD. Additionally, the IME design process includes provision for advanced alternatives for safe handling and removal of influxes within the limits of the primary barriers and those of the surface equipment.