Deepwater Drilling Made More Efficient and Cost-Effective Using the Microflux Control Method and an Ultralow Invasion Fluid to Open the Mud Weight Window
- Helio M. Santos (Impact Solutions Group Ltd.) | John W. McCaskill (Power Chokes) | Joseph I. Kinder (Secure Drilling LP) | Paul I. Reid (Impact Solutions Group Ltd.) | John R. Kozicz (Transocean Inc.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 2007
- Document Type
- Journal Paper
- 189 - 196
- 2007. Society of Petroleum Engineers
- 2 Well Completion, 1.7.1 Underbalanced Drilling, 1.8 Formation Damage, 1.6.1 Drilling Operation Management, 1.11 Drilling Fluids and Materials, 1.14 Casing and Cementing, 1.7.2 Managed Pressure Drilling, 4.1.5 Processing Equipment, 2.1.7 Deepwater Completions Design, 1.7 Pressure Management, 5.2 Reservoir Fluid Dynamics, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.3.2 Subsea Wellheads, 1.6.3 Drilling Optimisation, 5.7.5 Economic Evaluations, 4.3.4 Scale, 1.7.5 Well Control, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.6 Drilling Operations, 4.1.2 Separation and Treating, 5.8.3 Coal Seam Gas, 1.6.11 Plugging and Abandonment
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A common major challenge in deepwater drilling is the narrow margin between pore pressure and fracture gradient. In many basins, deepwater wells are becoming even more challenging, with subsalt and deeper horizons introducing problems that can lead to well abandonment before the target depth (TD) is reached. The key to drilling these wells safely and cost- effectively is to use technologies, methods, and procedures that allow the mud-weight window to be widened.
This paper describes two technologies that, when combined, can widen the effective mud-weight window significantly. One is the Micro-Flux Control (MFC) method. This is a closed-loop drilling system that allows the safe use of a mud weight as close as possible to the pore pressure. The other technology is an ultralow invasion-drilling fluid (ULIF) that increases the leakoff pressure of the openhole section, thereby opening the mud-weight window. Several field cases involving the drilling fluid are described, with increases of more than 1.5 lbm/gal in the leakoff pressure observed in wells in the Gulf of Mexico (GOM).
Results obtained with the MFC method at a test facility in the USA are described. These show the ability of the method to deal very effectively with any influx or loss.
Significant operational savings have already been obtained with the drilling fluid. However, the combination of the two technologies will produce a step change in safety, technical capability, and economics in many deepwater operations.
Wells with a narrow margin between pore pressure and fracture gradient are becoming more common. Not only is the geological environment where new reserves are often located becoming more complex, but the depletion of current fields is also creating increasing problems in development and infill wells. The situation becomes more complex in deep water, especially when operators are trying to locate reserves below salt layers, and in high-pressure/high-temperature (HP/HT) environments.
In many deepwater prospects, several casing strings (including contingency strings) have to be considered. However, many of these wells are still abandoned before reaching TD. These wells are extremely expensive, sometimes costing close to USD 100 million each. One operator in the GOM abandoned a well after spending more than USD 80 million. Another spent USD 120 million before abandoning the well. It is clear that the technical limit of conventional drilling is often encountered before achieving the ultimate goal of reaching TD to access hydrocarbon reserves. New technologies and methods must therefore be introduced to allow these new frontiers to be added to producible reserves in the near future.
This paper focuses on wells with narrow margins between the pore pressure and fracture gradient, highlighting two technologies that can reduce significantly the problems faced when drilling those wells. Even though the technologies can be used separately, the combination of the two in the same well can provide the optimum drilling solution.
The paper first addresses the MFC method and describes some of its unique capabilities for detecting influxes or losses at a very early stage. This allows the operator to trigger actions to detect and control a problem as it begins, and to prevent it from escalating to the point where the solution is costly and time consuming (sometimes forcing early abandonment). With the MFC method, the mud weight can be reduced as close as possible to the pore pressure in a very safe way. Thus, MFC deals with the left side of the mud-weight window—the pore-pressure curve.
This paper will then describe how to increase the leakoff pressure of the well, effectively widening the mud-weight window. The method of doing this by using a ULIF has been applied in many wells with extremely good results, while also giving big savings to operators. Field cases where the ULIF approach has been used are described.
|File Size||2 MB||Number of Pages||8|
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