An industry-supported research project has completed its evaluation of alternative initial responses to kicks taken during the constant bottom hole pressure (CBHP) method of managed pressure drilling (MPD) operations. The evaluation is the first phase of a study that is intended to provide a basis for comprehensive, reliable well control procedures for MPD operations. The evaluation was based primarily on computer simulations of multiple alternative initial responses to several causes and severities of kicks in different well geometries. Three responses were concluded to have general application: increasing casing pressure until flow out equals flow in, shutting the well in, and using an adaptation of an MPD pump shut down schedule to detect and shut in low rate kicks. A simple shut-in was concluded to be the most generally applicable response because it stops formation flow without requiring any special equipment. However, it also causes an increased risk of exceeding the formation fracture pressure for most situations versus a response that maintains continuous circulation. Increasing casing pressure while maintaining a constant pump rate until flow out equals flow in was concluded to be the most applicable response that avoids the disadvantages of shutting in the well. However, it requires accurate metering of return flow as a basis for determining whether formation flow has stopped. The adaptation of an MPD pump shut down schedule can be used to determine whether questionable kick indications are caused by a kick more conclusively than the other responses. It ends with the well being shut-in. A fourth response, increasing the pump rate, also has important but very limited application. The selection of which response is the most practical is shown to depend on well conditions and the equipment being used. Potential advantages of and constraints on the use of these responses are also explained.

Summary An industry-supported research project has completed its evaluation of alternative initial responses to kicks taken during the constant-bottomhole-pressure (CBHP) method of managed-pressure-drilling (MPD) operations. The evaluation is the first phase of a study that is intended to provide a basis for comprehensive, reliable well-control procedures for MPD operations. The evaluation was based primarily on computer simulations of multiple alternative initial responses to several causes and severities of kicks in different well geometries. Three responses were concluded to have general application: increasing casing pressure until flow out equals flow in, shutting the well in, and using an adaptation of an MPD pump-shutdown schedule to detect and shut in low- rate kicks. A simple shut-in was concluded to be the most generally applicable response because it stops formation flow without requiring any special equipment. However, it also causes an increased risk of exceeding the formation fracture pressure for most situations vs. a response that maintains continuous circulation. Increasing casing pressure while maintaining a constant pump rate until flow out equals flow in was concluded to be the most applicable response that avoids the disadvantages of shutting in the well. However, it requires accurate metering of return flow as a basis for determining whether formation flow has stopped. The adaptation of an MPD pump-shutdown schedule can be used to determine whether questionable kick indications are caused by a kick more conclusively than the other responses. It ends with the well being shut in. A fourth response, increasing the pump rate, also has important but very limited application. The selection of which response is the most practical is shown to depend on well conditions and the equipment being used. Potential advantages of and constraints on the use of these responses are also explained.

The constant bottom hole pressure (CBHP) method of managed pressure drilling (MPD) has important advantages versus conventional drilling, especially for well control. One is the ability to stop formation flow by increasing casing pressure while continuing to circulate rather than shutting in the well. A requirement for applying this method is for the pressure rating of the rotating control device to exceed the maximum casing pressure experienced during kick circulation. This peak casing pressure is typically estimated by applying the gas law for a single bubble calculation or by using a computer simulation. This paper describes a new, step wise method that combines gas law calculations with empirical knowledge developed by Ohara (1996) of gas distribution and velocity based on full-scale kick circulation experiments. The new method was applied to predict the maximum casing pressure expected during kick circulation for a range of well geometries, kick sizes, fluid properties, and circulating rates. The results of applying the new method were compared to single bubble calculations, transient multiphase computer simulations, and the actual pressures recorded in test wells. The proposed method provides a simple, potentially more accurate way to predict the maximum casing pressure during circulation of a gas kick. Consequently, it can be used to determine the surface equipment pressure ratings and formation fracture resistance required to provide the desired kick tolerance to drill safely using MPD equipment for well control.

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Large volume slick-water stimulations have become the de facto standard for completion strategy in the Upper Devonian, Marcellus, and Utica/Point Pleasant. Current completion optimization work has focused on optimizing stage spacing, sand loading, and injection rate which have shown increases in well productivity. One commonly overlooked variable in the design equation is stimulation fluid chemistry and rock/fluid interaction. Friction reducers, the primary additive of a slickwater system, have become a commodity with many service companies providing similar systems. Premium slickwater systems in the Marcellus are generally characterized by the ability to tolerate high percentages of produced water. We have developed an alternative approach to the design of stimulation fluid chemistry. This approach consists of creating a comprehensive laboratory workflow justification for multiple fluid combinations with consideration for specific thermal maturity windows. The laboratory workflow includes proprietary rock/ fluid interaction tests that insure formation compatibility, lever imbibition/displacement production mechanisms, insure compatibility of fluid components inclusive of available water sources, and insure optimization of the fluid based on stimulation intensity (Budney 2017) objectives. After extensive testing, a new stimulation fluid chemistry has been developed that offers several advantages verified by laboratory testing. The new stimulation fluid chemistry consists of a multifunctional additive with the following characteristics: salt tolerant, viscosifying, formation stabilizing, wettability enhancing friction reducer technology paired with a compatible scale inhibitor and biocide. This new stimulation fluid chemistry was field tested against an incumbent fluid chemistry provided by the stimulation service company. Well production data from the first multiple well experiment demonstrated the new stimulation fluid chemistry resulted in significantly improved well performance. A second multi-well experiment in a different area was conducted and proved the well performance improvement associated with the new stimulation fluid chemistry was repeatable. Economic analyses on wells from both field experiments demonstrate an excellent return on investment with the new stimulation fluid chemistry. This study highlights the importance of justifying stimulation fluid chemistry utilizing a laboratory workflow. The laboratory workflow incorporates rock/fluid interaction testing to maximize the imbibition/displacement production mechanism. The laboratory workflow must also prove that the stimulation fluid chemistry satisfies the stimulation intensity objectives of high rate, high sand concentration, and reduced fluid volumes while enabling reliable field execution.