Evolution of the MPD Operations Matrix: The Influx Management Envelope

Abstract

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.

The Influx-Management Envelope Considering Real-Fluid Behavior

“…Although the resulting IME from the proposed method show more margins with respect to acceptable kick size than the original IME equations by Culen et al (2016) if using a real-gas EOS, it is not the authors belief that the result is un-conservative, especially if a methane gas kick at bottom and single bubble is assumed. The main reason for having more margins is the inclusion of a real gas EOS.…”

“…The concept of considering a kick envelope and comparing the link between this and the WCM was performed by Mir Rajabi, Hannegan, and Moore 2014 using a high fidelity simulator. In the original IME paper, Culen et al (2016) does simplifications to make calculation of this kick envelope curve explicit and analytically solvable. Gabaldon et al (2017) shows that this approach might be overly conservative by comparing this to a high fidelity simulator.…”

“…The calculation of this "limit line" is the core of the IME, and the position of the limit line will be significantly affected by the chosen simplifications. The equation presented in Culen et al (2016), Eq.2 assumes ideal gas, gas kick at the bottom and incompressible liquid. Eq.…”

“…The original IME paper by Culen et al (2016) assumes ideal gas in the mass balance equation, this is to account for the gas expansion in the gas bubble. Second, for the pressure equation, gas and liquid densities are assumed to be constant such that ρ g = ρ g (p B ) = ρ g (p D ) = const and ρ l = ρ l (p B ) = ρ l (p D ) = const.…”

“…Well configuration for the two test wells are summarized in Table 2. 2by Culen et al (2016). Bottomhole temperature is set to 250°F and return flow temperature to 150°F for all cases.…”