Experimental Study on Cuttings Transport With Foam Under Simulated Horizontal Downhole Conditions
- Zhu Chen (Shell E&P Co.) | Ramadan M. Ahmed (U. of Tulsa) | Stefan Z. Miska (U. of Tulsa) | Nicholas E. Takach (U. of Tulsa) | Mengjiao Yu (U. of Tulsa) | Mark B. Pickell (U. of Tulsa) | John H. Hallman (Weatherford International Ltd.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- December 2007
- Document Type
- Journal Paper
- 304 - 312
- 2007. Society of Petroleum Engineers
- 4.1.9 Tanks and storage systems, 1.6.6 Directional Drilling, 5.4.2 Gas Injection Methods, 2 Well Completion, 4.6.3 Gas to liquids, 1.7.2 Managed Pressure Drilling, 2.5.2 Fracturing Materials (Fluids, Proppant), 4.3.4 Scale, 5.5.11 Formation Testing (e.g., Wireline, LWD), 1.11 Drilling Fluids and Materials, 4.1.5 Processing Equipment, 1.7.1 Underbalanced Drilling, 4.1.6 Compressors, Engines and Turbines, 4.2 Pipelines, Flowlines and Risers, 1.7.6 Wellbore Pressure Management, 5.4 Enhanced Recovery, 4.1.2 Separation and Treating, 1.10 Drilling Equipment, 4.6 Natural Gas, 1.7.7 Cuttings Transport, 2.7.1 Completion Fluids, 1.6 Drilling Operations, 3 Production and Well Operations
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The use of drilling foams is increasing because foams exhibit properties that are desirable in many drilling operations. A good knowledge of cuttings transport efficiency under downhole conditions is essential for safe and economical foam drilling. Previous cuttings transport studies with foam are limited to low pressure and ambient temperature conditions. No experimental study has been conducted under downhole (i.e., elevated pressure and temperature) conditions. This paper presents an experimental study of cuttings transport with foam in a horizontal annulus under simulated downhole conditions.
Experiments were conducted to determine the effects of polymer additives, foam quality, flow velocity, temperature, and pressure on foam cuttings transport. Experiments were carried out at elevated pressures (100 to 400 psi) and temperature (80?to 170 degrees F) conditions in a unique full-scale flow loop with a 73-ft long test section (5.76 × 3.5 in. concentric annulus). A field-tested commercial foam system consisting of surfactant (1% v/v) and hydroxylethylcellulose polymer (HEC) was used in the experiments. Three different polymer concentrations (0.0, 0.25, and 0.5% v/v) were tested. Foam quality was varied from 70 to 90%.
During a test, cuttings were injected continuously to the flow loop until a steady state condition was established in the test section. In-situ cuttings volumetric concentration (i.e., the ratio of the volume of cuttings in the suspension and the cuttings bed to the volume of the annulus) in the test section was determined using nuclear densitometers, load cell measurements, and by weighing cuttings flushed out of the flow loop. Test parameters recorded during the experiments were: liquid and gas injection rates, cuttings weight in injection and removal towers, mixture density, friction pressure loss, and pressure and temperature in the annulus.
Two flow patterns, stationary cuttings bed, and fully suspended flow, were observed during the cuttings transport tests. The flow pattern depends on polymer concentration, foam quality, and annular velocity. Annular flow velocity, foam quality, and polymer concentration all affect cuttings transport efficiency and frictional pressure loss. This paper will help to better design foam drilling and cleanup operations.
Foam is a highly attractive alternative over conventional drilling fluid because it has low density and flexibility in ECD control. However, it is difficult to obtain reliable predictions of ECD for foam drilling because of the complexity of foam flows. When drill cuttings are present in the wellbore, the foam-cuttings mixture affects bottomhole pressure (BHP) and this makes the already complicated compressible foam flow even more complex. Therefore, cuttings transport with foam should be well understood for accurate BHP and ECD estimations. In short, a good knowledge of foam hydraulics and cuttings transport is necessary for safe and economical drilling.
Studies on cuttings transport using foam fluids are very limited. Though cuttings in foam affect hydraulics calculations and ECD predictions, it is generally accepted that foam is very efficient in cuttings transport in vertical wells. Foam flow velocity with 120 ft/min is sufficient for most vertical well foam drilling; in some cases, flow velocity as low as 70 ft/min has been reported successful. For foam drilling in horizontal wells, the situation is quite different compared with that in vertical wells because the particle settling velocity is perpendicular to foam flow direction so that drill cuttings tend to settle to the low side of the wellbore; and the density of drill cuttings is much higher than the density of foam. As a result, the mechanisms that govern cuttings transport are different for horizontal wells. Empirical correlations and models developed for vertical wells may not be valid for horizontal and inclined wellbores (Chen 2005).
Although experiments on cuttings transport with foam in horizontal wells with a large-scale flow loop have been conducted recently (Ozbayoglu 2002; Capo 2002; Martins et al. 2000; Miska et al. 2004), tests were performed under low pressure and ambient temperature conditions. No experiments have been conducted on cuttings transport with foam under elevated pressure and temperature conditions. Therefore, this research project is unique in terms of cuttings transport with foam. There is a definite need for this kind of study to better understand cuttings transport with foam in simulated downhole conditions, and for more reliable BHP and ECD predictions.
|File Size||1 MB||Number of Pages||9|
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