From Lean to Extreme-Lean Well Profile: Field Experience in the Mediterranean Sea
- A. Calderoni (Eni SpA.) | Franco Donati (Eni SpA.) | Paolo Ferrara (Eni SpA.) | Michele Maestrami (Belayim Petroleum Company) | Joachim Oppelt (Baker Hughes) | Sven Krüger (Baker Hughes)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- March 2010
- Document Type
- Journal Paper
- 19 - 26
- 2010. Society of Petroleum Engineers
- 1.6 Drilling Operations, 1.1 Well Planning, 2.1.7 Deepwater Completions Design, 1.6.6 Directional Drilling, 1.14 Casing and Cementing, 1.12.2 Logging While Drilling, 1.6.1 Drilling Operation Management, 2 Well Completion, 1.1.6 Hole Openers & Under-reamers, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.5 Drill Bits, 2.3 Completion Monitoring Systems/Intelligent Wells, 1.6.10 Running and Setting Casing, 1.10 Drilling Equipment, 1.12.6 Drilling Data Management and Standards
- Mediterranean Sea, reaming, directional drilling, extreme lean casing, cost reduction
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The main subject of this paper will be to outline the field experience achieved with a new type of well profile and directional drilling system. Reducing the cost of well construction has been a driver for many new technologies. The lean casing profile introduced by Eni SpA, the major Italian oil and gas company, about a decade ago was a successful step towards lowering the drilling and completion cost in the vertical, top-hole section. Automated vertical-drilling tools have been the technical enabler of such a concept. Recently, this oil company has moved further towards an even more radical "extreme-lean well profile." This paper gives a brief insight into the well-design concept and the enabling technology behind it. The drilling technology is based on the well-known automated vertical-drilling system, which has been enhanced by the capability to drill an enlarged hole size below a casing without compromising the verticality and hole quality. In the main part of the paper, two field applications, in the Mediterannean Sea and offshore Egypt, are described. The paper will also cover the lessons learned especially from the second of the first two field applications. The extreme-lean well profile and automated vertical-reaming technology can provide value to several drilling campaigns not only through the reduction of well-construction cost. Another major benefit is the ability to run an intermediate casing string, if required because of difficult well conditions, and still arrive at the same diameter of casing in the reservoir. The completion concept and the enabling tool technology are very unique and have not been available to the industry until recently.
It is the ultimate purpose of any oil and gas well to help develop a reservoir as soon as possible and with the maximum rate and volume of hydrocarbon recovery. Reaching the reservoir horizon quickly and safely requires, in many cases, the application of some smart well-construction techniques. This is true even in the upper sections of the hole. A straight and smooth borehole curvature reduces the inherent risks of running casing strings. In addition, such geometry provides the optimum conditions for being able to drill the horizontal section to the maximum reach (Calderoni et al. 1998). At the same time, when the trajectory is of a "gun-hole" shape and quality, less annular space has to be reserved for the casing string running operation. If this concept is realized through all or most of the hole sections, the well will be less cascaded than with the conventional approach. This type of "lean casing profile" allows for faster well construction, fewer consumables and an increased operational efficiency. The lean-casing-profile concept was first introduced to the oil field in the early 1990s. Based on the economic success achieved, the operating company has recently decided to drive this concept even further. The new extreme-lean casing profile reduces the annular gap even further than with the previous method. In a way, the extreme-lean shape is an important step towards the visionary monobore hole, yet much more realistic to do as of today. As with the previous method, this new well construction scheme is based heavily on the application of an enabling downhole technology that guarantees the required straightness and precision. This can be accomplished by means of an automated rib-steering directional-drilling device that is fully operated in the sliding mode. In a hole's vertical section, eliminating drillstring rotation improves borehole stability. To facilitate the extreme-lean casing well construction, some new downhole directional-drilling systems had to be created, such as an automated steering system with an integrated reamer and an automated rib-steering device with a special diameter. The new well construction process and made-for-purpose tools have been field tested in a series of wells in the Egyptian Sea where operating conditions were critical because of hole-stability problems.
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Calderoni, A., Freyer, C., Donati, F., Butté, L., and Oppelt, J. 2007.Automated Vertical Reaming Technology Facilitates First Application of ExtremeLean Casing Profile. Presented at the Offshore Mediterranean Conference andExhibition, Ravenna, Italy, 28-30 March.
Calderoni, A., Ligrone, A., and Molaschi C. 1999. TheLean Profile: A Step Change in Drilling Performance. Paper SPE 52788presented at the SPE/IADC Drilling Conference, Amsterdam, 9-11 March. doi:10.2118/52788-MS.
Calderoni, A., Oppelt, J., Ligrone, A., Trampini, A., and Gauld, S. 1998. Automated Steering Systems Applied toComplex Horizontal Well in South Italy. Paper SPE 50379 presented at theSPE International Conference on Horizontal Well Technology, Calgary, 1-4November. doi: 10.2118/50379-MS.