Calculations of Equivalent Circulating Density in Underbalanced Drilling Operations
- Reza Ettehadi Osgouei (The University of Tulsa) | William Liew Sin Yoong (PETRONAS Carigali Sdn. Bhd.) | Evren M. Ozbayoglu (University of Tulsa)
- Document ID
- International Petroleum Technology Conference
- International Petroleum Technology Conference, 26-28 March, Beijing, China
- Publication Date
- Document Type
- Conference Paper
- 2013, International Petroleum Technology Conference
- 4.1.2 Separation and Treating, 1.8 Formation Damage, 5.4.2 Gas Injection Methods, 5.8.6 Naturally Fractured Reservoir, 1.7.1 Underbalanced Drilling, 4.1.5 Processing Equipment, 1.6 Drilling Operations, 1.7.5 Well Control, 1.11 Drilling Fluids and Materials, 4.6 Natural Gas, 1.7.7 Cuttings Transport, 1.10 Drilling Equipment, 1.7.2 Managed Pressure Drilling, 5.4 Enhanced Recovery, 5.3.2 Multiphase Flow
- Underbalanced drilling using gasified liquid
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Underbalanced drilling using gasified fluids is one of the most widely usedmethods to drill depleted, low pressure and highly fractured formations. Forensuring a safe and successful underbalanced drilling operation, accurateprediction of the equivalent circulating density (ECD) is very important.Nevertheless, estimating ECD of gasified fluids is not easy due to thecomplexity of the two-phase fluid flow inside the wellbore. In this study,there are two major focuses considered; i) validation of the accuracy of Beggs& Brill (1973) model on the prediction of pressure losses of gasifiedfluids in underbalanced drilling operation, and modification of Beggs &Brill (1973) model for pressure loss estimation inside the wellbore, and ii) topropose an ECD calculation procedure for gasified fluids by using modifiedBeggs & Brill (1973) model.
Tovalidate the accuracy of Beggs & Brill (1973) model, experiments werecarried out using Middle East Technical University (METU) Cuttings TransportFacility to obtain the pressure losses of gasified fluids in an annulus andtheir corresponding flow patterns. Air-water mixtures were used with variousin-situ air and water flow velocities of 0-120 ft/s and 0-10 ft/s,respectively, at wellbore inclinations of 90°, 75°, 60°, 45° and 12.5° withoutinner pipe rotation. Pressures were recorded at several points along theannular test section, and pressure distribution along the test section wasmeasured. Meanwhile, flow patterns were determined by the help of a high speeddigital camera.
Resultsshowed that although Beggs & Brill (1973) model can estimate pressurelosses in low gas and liquid flow rates and low slip ratio between two phasesfor horizontal and near horizontal annular sections with a reasonable accuracy,this model cannot accurately calculate pressure losses at inclined and verticalannular sections. With some modifications, improved Beggs & Brill (1973)model (by applying suggested procedure) can be used to predict ECD and annularpressure losses of gasified fluids inside the annulus accurately. Thisinformation can be directly applied for underbalanced drilling operations whengasified fluids are used.
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