Computer-Aided Real-Time Kick Analysis and Control
- S.I. Jardine (Sedco Forex Schlumberger) | D.B. White (Sedco Forex Schlumberger) | John Billingham (Schlumberger Cambridge Research)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 1994
- Document Type
- Journal Paper
- 199 - 204
- 1994. Society of Petroleum Engineers
- 1.6.1 Drilling Operation Management, 1.7 Pressure Management, 3 Production and Well Operations, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.10 Drilling Equipment, 1.11 Drilling Fluids and Materials, 4.1.4 Gas Processing, 1.6 Drilling Operations, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.7.5 Well Control, 2.2.2 Perforating, 4.3.4 Scale, 5.4.2 Gas Injection Methods
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After early kick detection, the most important activities during well-control operations are correct identification of shut-in pressures, preparation of the kill plan, and careful monitoring of the kill operation. This paper describes the development and application of techniques to analyze and to extract the maximum amount of information from surface pressure measurements during shut-in.
Early detection of an influx (or "kick") from the formation being drilled is generally recognized as a key consideration for rig safety and has led to the development of reliable kick-detection methods. Following detection of the kick, however, the critical and potentially hazardous operation of circulating out the influx remains. After the well has been shut in, considerable information can be gleaned from analysis of surface pressure measurements by applying the appropriate processing techniques. This allows crucial parameters to be determined automatically, passed to the driller for verification, and used to generate a kill plan. In addition, information can be obtained that leads to an accurate estimate of annular pressure at the weakest point in the well. Numerical analysis techniques can be used to determine the shut-in parameters and, in particular, provide (1) accurate, automatic detection of stabilized shut-in pressures; (2) an improved method for computing influx density that is effective even for horizontal wells; and (3) shoe-pressure prediction by use of a kill model that is initialized by the shut-in measurements.
These measurements can be combined with conventional well-control techniques to generate automatically a kill plan that has been developed to give improved pressure control for horizontal and highly deviated wells. The analyses are intended for use with water-based muds. Although certain aspects are equally valid for oil-based muds, we assume that water-based mud is deployed and that the bit is at, or near, the bottom of the well. The following describes the sequence of analyses that enable the appropriate information to be extracted from conventional rig measurements.
During drilling and circulating operations, continuous monitoring of active system volume and differential flow (flow out minus flow in) is essential for rapid and reliable kick detection. These measurements are complementary because differential flow gives the fastest indication of a rapid kick, whereas pit levels, which are sensitive to the integral of differential flow, enable the detection of slower influxes. For the subsequent well-control operation, the estimated kick volume is an important parameter; therefore, it is useful if kick-detection techniques also provide an accurate estimate of influx volume when the blowout preventer (BOP) is closed.
Following closure of the BOP, a curve can be fitted to the active tank volume data recorded before the pumps were switched off to obtain information on the influx flow rate that is required as input for the subsequent analyses. If the influx is rapid, however, very little pit gain may occur until after the pumps have stopped, which may result in the pit gain being lost in the flowback volume of the return lines. In this case, delta-flow measurements can be used if they are processed to ensure a reliable kick indication. Methods of ensuring this, even under conditions of severe rig heave, are available. The use of backup and normally redundant analysis as part of the kick-detection strategy greatly increases the robustness of the overall detection system.
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