Formation of Underwater Cuttings Piles in Offshore Drilling
- Qian Fang (University of Louisiana at Lafayette) | Boyun Guo (U. of Louisiana at Lafayette) | Ali Ghalambor (U. of Louisiana at Lafayette)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- March 2008
- Document Type
- Journal Paper
- 23 - 28
- 2008. Society of Petroleum Engineers
- 1.6 Drilling Operations, 1.11 Drilling Fluids and Materials, 2 Well Completion, 6.5.2 Water use, produced water discharge and disposal, 1.7.7 Cuttings Transport, 4.3.4 Scale
- 1 in the last 30 days
- 592 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 12.00|
|SPE Non-Member Price:||USD 35.00|
The discharge of drill cuttings to the seabed can significantly reduce offshore drilling cost. However, the formation of cuttings piles on the seabed near the rig site can present problems for drilling and production operations. When the problem is likely to occur in the areas of low-current velocity, the cuttings are not discharged to seabed, but ground and injected to formation or transported to the onshore for disposal, which increases drilling cost. It is highly desired to have an accurate method to predict the location and configuration of the cuttings piles in the design stage of well drilling. This paper presents a solution to the problem.
Starting from Newton's second law of motion, a mathematical model has been developed in this study to predict the location, configuration, and characteristics of cuttings piles. Factors considered include water depth, current velocity, cuttings properties (e.g., size distribution, density, and sphericity), and water properties (such as density and viscosity). This mathematical model has been computerized. It provides well planners a useful tool for predicting the characteristics of cuttings piles during drilling. Application of the tool can reduce the cost of drilling through better handling of drill cuttings such as discharging to water vs. injecting into the formation.
There are three basic types of fluids that are currently used for drilling oil and gas wells. They are water-based mud (WBM), oil-based mud (OBM), and synthetic-based mud (SBM). Historically, most wells in U.S. waters have been drilled with WBM. Water-based mud and its associated cuttings usually are permitted for discharge in federal waters. Because of their adverse environmental effects, OBM and its associated cuttings have never been permitted for discharge in U.S. waters. Synthetic-based muds are designed to be less toxic and to biodegrade in marine sediments faster than OBM. Discharge of SBMs is not permitted except for small amounts associated with cuttings.
At offshore platforms, most WBM- and SBM-associated cuttings are discharged to the seabed whenever feasible. If the discharge of cuttings is not an option, cuttings handling will become extremely complicated. The volume of slurry to be re-injected to the formation may increase by a factor of 3 to 6, however, in several cases the formation may not be able to receive such a large volume during a short time interval. Land-based handling of cuttings contaminated with WBM is difficult. Burning off the chemicals and distillation of water are power consuming. All processes involved in the disposal or recycling of these residual drilling materials will have an environmental impact, not necessarily from discharges to the sea or ground, but resulting from the emission of different gases like CO2 to the air.
The formation of cuttings piles on seabed near the rig site can present problems for drilling and production operations. If the water is too shallow, or the current velocity is too low, cuttings piles will grow up to the discharge point and plug the discharging device. When these problems are likely to occur, the cuttings are not discharged to seabed, but ground and injected to the formation, or transported to onshore for disposal. Both options increases drilling cost. Currently, engineers predict whether the problem is likely to occur or not on the basis of very rough calculations. Because the decision between discharging cuttings to the seabed vs. injecting into the formation, or transporting to onshore all have strong impacts on drilling cost, it is highly desirable to have an accurate method to predict the location and configuration of the cuttings piles on the seabed under different conditions.
|File Size||916 KB||Number of Pages||6|
Bourgoyne, T.A., Chenevert, E.M., Millhein, K.K., and Young, S.F. 1986.Applied Drilling Engineering. Textbook Series, SPE, Richardson, Texas 2:173-175.
Brandsma, M.G. 2004. Automatic Validation ofthe Offshore Operators Committee Discharge Model and Application to PredictingDrilling Solids Accumulation on the Sea Floor. Environmental Modelingand Software 19 (7-8): 617-628. doi:10.1016/j.envsoft.2003.08.002.
Brandsma, M.G., Smith, J.P., O'Reilly, J.E., Ayers, R.C. Jr., and Holmquist,A.L. 1992. Modeling Offshore Discharges of Produced Water. In ProducedWater, ed. J.P. Ray and F.R. Engelhart, 59. New York City: PlenumPress.
Dorf, R.C. 1996. The Engineering Handbook, 1021-1022. Boca Raton,Florida: CRC Press and IEEE Press.
IESL. 2003. SizeCUTTM. Innovative Engineering Systems LimitedTechnical Brochure, March.
McFarlane, K. and Nguyen, V.T. 1991. The Deposition of Drill Cuttings onthe Seabed. Paper SPE 23372 presented at the SPE Health, Safety andEnvironment in Oil and Gas Exploration and Production Conference, The Hague,11-14 November. doi: 10.2118/23372-MS
Nedwed, T. 2004. Best Practicesfor Drilling Cuttings and Mud Discharge Modeling. Paper SPE 86699 presentedat the SPE International Conference on Health, Safety, and Environment in Oiland Gas Exploration and Production, Calgary, 29-31 March. doi:10.2118/86699-MS
Nedwed, T.J., Smith, J.P., and Brandsma, M.G. 2004. Verification of the OOCMud and Produced Water Discharge Model Using Lab-Scale Plume BehaviorExperiments. Environ. Model. & Software 19 (7-8):655-670. doi: 10.1016/j.envsoft.2003.08.004.
Nedwed, T.J., Smith, J.P., and Melton, H.R. 2006. Fate of Nonaqueous Drilling-FluidCuttings Discharged From a Deepwater Exploration Well. Paper SPE 98612presented at the SPE International Conference on Health, Safety, andEnvironment Conference, Abu Dhabi, U.A.E., 2-4 April. doi: 10.2118/98612-MS
Smith, J.P., Brandsma, M.G., and Nedwed, T.J. 2004. Field Validation of theOffshore Operators Committee (OOC) Mud and Produced Water Discharge Model.Environ. Model. & Software 19 (7-8): 739-749. doi:10.1016/j.envsoft.2003.08.007.
Stokes, G.G. 1845. On the theories of the internal friction of fluids inmotion and of the equilibrium and motion of elastic solids. Trans.,Cambridge Phil. Soc. 8: 287-305.
Stokes, G.G. 1851. On the effect of internal friction on the motion of apendulum. Trans., Cambridge Phil. Soc. 9: 8-106.