- Table: Slimhole vs. conventional drilling. The physical and economic advantages of slimhole drilling in deepwater, versus that of conventional drilling. (This information was presented by Thorlief Enger of Norsk Hydro at the OSEA Conference in Singapore.)
Moored production tanker becoming system of choice
The moored tanker production system is becoming the system of choice for many deepwater field developments because of favorable experiences with existing applications and the recent development of efficient connection assemblies. Here is the outlook:
- Quick release technology: The ability to release from and reconnect to submerged mooring assemblies when needed has cut nearly 30% of development costs of a single field and more when the vessel is re-used.
- Better permanent mooring: Alternatively, improved bow designs for proposed tankers and dynamic positioning are reducing the impact of waves on the swivel assembly, eliminating the need to disconnect in rough weather.
- Production storage: The need for bulk storage of produced fluids favors a tanker shape. A tanker system allows economic development of fields far from pipelines or other platforms, increasingly the situation facing new developments today.
- Inhibiting methods: Deepwater development is showing a high incidence of hydrates and paraffins. The inhibition solutions are thermal, which requires power generation, or chemical, which requires large quantities of injection fluids.
- Mobility: The mobility of a floater production unit will become increasingly important as field sizes dwindle and production periods shorten. Also, tanker production units can be easily converted for extended well testing programs.
- Tanker availability: The supply of tankers available for conversion, the apparent lower cost of conversion, and the lower cost of the mooring system favors the monohull for all developments save those with high production flows, a large number of wells, large volume water or gas injection needs, or high workover requirements.
Semisubmersible and spar-shaped floaters will also play a role in field developments, but lack the storage capacity of monohulls and are frequently weight sensitive. High on the technology wish list for tanker production units are larger swivel joints with higher oil and gas throughputs and provisions for injection.
London consultant Smith Rea, with some justification, has predicted the number of floating production systems will double in the next six years. Most of the growth will come in the Pacific Rim where pipeline transportation is sparse.
OTC featuring papers on deep pipelines, subsalt, VIV, hydrates, buckets
Among the major topics generating a great deal of interest in the 1995 Offshore Technology Conference are sessions or technical paper collections on the following subjects:
- Oman-India gas pipeline: No topic has generated so much interest in the investigation stage as this pipeline transiting 11,500-ft depths across the Arabian Sea. Various papers will probe the geotechnology, pipelaying methods, hydro-dynamic aspects, and wall sizing.
- VIV suppression: Shell is dealing with tremendous shearing currents (vortex-induced vibration) on long tubulars for several deepwater developments in the US Gulf of Mexico. Various papers will deal with the physics of shear flow across long risers, vortex suppression methods, and the sizing of helical strakes to combat the motion.
- Subsalt exploration: Geoscientists and drilling engineers are building experience on many aspects surrounding subsalt formations. Various papers will exploit the technical and geomechanical aspects of salt drilling.
- Hydrates and waxes: Paraffin and hydrate formations are becoming a major deepwater hurtle and a number of papers deal with the conditions leading to their formation and some solutions, including kinetic inhibition.
- Bucket foundations: Large bucket-like suction feet at the base of jacket legs are proving to be an effective substitute for pilings in North Sea applications. The buckets are able to withstand tension and compression loading. Test and applications data and results on the bucket systems will be presented in several papers.
164 extended reach wells drilled by 12 major operators
Amoco Production (ETPG, Drilling in Houston) has compiled a list of 164 extended reach wells drilled by 26 operators worldwide over the past 10 years who are active in extended reach drilling. The list was incomplete at press time and Amoco expected the list to grow. The list is as follows, beginning with the most active operator: !-- The following table has been generated by the Internet Assistant Wizard for Microsoft Excel. You can find this add-in on "http://www.microsoft.com/msoffice/freestuf/msexcel/index.htm" -- !-- ------------------------- -- !-- START OF CONVERTED OUTPUT -- !-- ------------------------- --
|Operator:||No. of wells:|
Included in the list were categories listing throw (lateral distance), measured distance, true vertical depth, location, and spud date. The wells are ranked by throw. Thus far the leader in well throw is BP, with a throw of 25,000 ft at Wytch Farm (onshore to offshore) in England. Following immediately behind were Statoil and Norsk Hydro, who are both active in drilling record breaking extended reach wells in the Norwegian Sector of the North Sea.
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