MPD Operation Research Articles

High-Density Drilling Fluids for Managed Pressure Drilling: Lab Development and Field Trial

Abstract Managed pressure drilling (MPD) offers a closed-loop circulation system in which formation fracture pressure, bottom hole pressure, and pore pressure are considered and managed at surface. The right choice of drilling fluid used during MPD operation facilitates proper mud management and treatment. Lab formulation and field trial of a high-density water-based drilling fluid comprising a mixture of barite (BaSO4) and manganese tetroxide (Mn3O4) as weighting agents have been described in this paper. Drilling fluids having a mixture of Mn3O4 and BaSO4 as weighting agents would have lower equivalent circulating density (ECD), better sag, better acid solubility, and lower fluid cost as compared to conventional BaSO4-based fluids. This paper describes the formulation of three different water-based drilling fluids viz. 100, 120, and 150 pcf drilling fluids having a mixture of Mn3O4 and BaSO4 and hot rolled at temperatures of 270, 250, and 300 °F, respectively. Rheological properties, sag resistance, and high pressure-high temperature (HPHT) filtration properties of the three fluids have been described in the paper. Data obtained from the field trial of 160 pcf high-density drilling fluids having a mixture of Mn3O4 and BaSO4 for wells with a 300 °F bottom hole static temperature have been described. HPHT operations across naturally fractured formations with 0.5–1.0 pcf drilling fluid window have been described in the paper. During the field trial, the fluid having a mixture of Mn3O4 and BaSO4 showed good rheological, filtration, and sag properties thereby resulting in successful drilling of the well with no issues. MPD operation became more successful and practical with high-density drilling fluids having a mixture of Mn3O4 and BaSO4 as it facilitated better drilling fluid management and treatment in comparison to conventional fluids.

Influence of Gas Solubility on Zero Gas Flow Characteristics in MPD Operation

In this paper the authors have put forward the concept of annular zero gas flow and developed the residual gas model, considering the parameters of gas solubility, slippage, and the oil-based drilling fluid volume coefficient [1-3]. The calculation results show that in the process of continuous gas influx at the bottom of the well, the phenomenon of annular zero gas flow can be defined in terms of gas solubility [4-6]. The increase in the back pressure, the decrease in the gas invasion rate, and the decrease in the oil-based ratio can cause an increase in the length of the annular zero gas flow well section. When the back pressure increases from 0.1 to 4.0 MPa, the length of the annular zero gas flow section increases from 1000 to 2700 m. If the zero gas flow is not taken into consideration, the maximum error of the annular void ratio is 21.22% [7-10]. When the CO2, gas invades the bottom of the well, the oil-based ratio increases from 0.1 to 5, the length of the annular zero gas flow section increases from 1500 to 2250 m, and the maximum error of the annular void ratio is 26.57%.

Performance of Quasi-Steady MPD Thrusters at High Powers

T familiar axisymmetric MPD thruster is considered with a conical tungsten tip cathode, (-|, |, and f in. diam), and a copper plate anode-orifice, (2, 3, and 4 in. diam). The performance of such thrusters is investigated, with millisecond pulses, over a wide range of experimental conditions. The five noble gases are used as propellants, at flow rates in the range 0.1 to 100 g-sec. MPD currents 5 to 50 ka are employed and the corresponding input powers are in the range 0.1 to 10 Mw. Thrust is determined from impulse measurements with wellknown current waveforms, while instantaneous measurements are made for all other variables: m, J, and V, flow rate, current and voltage. A detailed analysis of the experimental results shows that the MPD performance is limited by a critical value of (J/m), which depends only on MPD geometry and on propellant properties. MPD operation, beyond the critical point, becomes increasingly objectionable on account of instabilities, sharp rise of the voltage, erosion and participation of spurious propellant. At the limit of credible MPD operation, the specific impulse depends on propellant properties only, and varies from about 3000 sec for lighter propellants, to about 400 sec for heavier propellants. In the same range, the maximum credible MPD efficiency varies from about 30% to about 10%. However, the efficiency depends on other MPD conditions also.

Some Experiments on the "Spoke" Phenomenon in MPD Operation

Abstract : The problem of the appearance of a current spoke in MPD operation has attracted an increasing interest. It is the question of whether the current transfer to the anode occurs in an axisymmetric way or whether the current, or part of it, concentrates in a spoke that rotates, in other works, whether a more or less significant rotating disturbance exists. It is concluded that a spoke must not necessarily exist. Transition to the spoke from axisymmetry seems to happen gradually as destabilizing effects grow. Also we doubt whether the appearance of a rotating disturbance in current transition will necessarily entail serious deviation from axisymmetry of the downstream regions. (Author)

Some experiments on the ''spoke'' phenomenon in MPD operation.

Some experiments on the ''spoke'' phenomenon in MPD operation.