Deep Water Production Research Articles

A Review of Strategies for Solving Gas-Hydrate Problems in Subsea Pipelines

Flow assurance management is critical to successful and economic operation of oil and gas production systems. As production activities progress into deeper waters, flow assurance challenges become more prevalent, and system design must address these issues from a fresh perspective. Hence, new management and remediation techniques have to be developed to reliably, efficiently, safely, and economically prevent or handle these problems for the range of expected conditions including startup, shutdown, and turndown scenarios. An inherent problem with natural gas production or transmission is the formation of gas hydrates, which can lead to safety hazards to production/transportation systems and to substantial economic risks. Therefore, an understanding of how, when, and where hydrates form is necessary to overcoming hydrate problems. These questions have become all the more crucial since deepwater fields have been discovered or brought in production, where these fields are perfect candidate to encounter hydrate forming conditions. This article answers these crucial questions as well as provides significant information on the best method to prevent and remediate hydrates in deepwater production operations.

Oil biodegradation by Bacillus strains isolated from the rock of an oil reservoir located in a deep-water production basin in Brazil

Sixteen spore forming Gram-positive bacteria were isolated from the rock of an oil reservoir located in a deep-water production basin in Brazil. These strains were identified as belonging to the genus Bacillus using classical biochemical techniques and API 50CH kits, and their identity was confirmed by sequencing of part of the 16S rRNA gene. All strains were tested for oil degradation ability in microplates using Arabian Light and Marlin oils and only seven strains showed positive results in both kinds of oils. They were also able to grow in the presence of carbazole, n-hexadecane and polyalphaolefin (PAO), but not in toluene, as the only carbon sources. The production of key enzymes involved with aromatic hydrocarbons biodegradation process by Bacillus strains (catechol 1,2-dioxygenase and catechol 2,3-dioxygenase) was verified spectrophotometrically by detection of cis,cis-muconic acid and 2-hydroxymuconic semialdehyde, and results indicated that the ortho ring cleavage pathway is preferential. Furthermore, polymerase chain reaction (PCR) products were obtained when the DNA of seven Bacillus strains were screened for the presence of catabolic genes encoding alkane monooxygenase, catechol 1,2-dioxygenase, and/or catechol 2,3-dioxygenase. This is the first study on Bacillus strains isolated from an oil reservoir in Brazil.

Chain of Custody for Samples of Live Crude Oil Using Visible—Near-Infrared Spectroscopy

In order to design oil production facilities and strategies, it is necessary to acquire crude oil samples from subsurface formations in oil wells in so-called openhole prior to production. In some environments, such as deepwater production of oil, decisions of huge economic importance are based on such samples. To date, there has been little quality control to verify that the crude oils collected in the sample bottles and analyzed up to a year later in the laboratory have any relation to the actual crude oils in the subsurface reservoirs. These high-pressure samples can undergo myriad deleterious alterations. Here, we introduce the chain-of-custody concept to the oilfield. The visible-near-infrared spectrum of the crude oil is measured in situ in the wellbore at the point of sample acquisition. This spectrum is compared with the spectrum measured on putatively the same fluid in the laboratory at the start of laboratory sample analysis. First, quantitative assessment is made of whether the fluid in the (high-pressure) sample bottle remains representative of formation fluids. Second, any specific changes in the spectrum of the fluid can be related to possible process control failures. Here, the entire process of chain of custody is proven. The chain of custody process can rapidly become routine in the petroleum industry, thereby significantly improving the reliability of any process that depends on fluid property determination.

The biodiversity of the deep Southern Ocean benthos

Our knowledge of the biodiversity of the Southern Ocean (SO) deep benthos is scarce. In this review, we describe the general biodiversity patterns of meio-, macro- and megafaunal taxa, based on historical and recent expeditions, and against the background of the geological events and phylogenetic relationships that have influenced the biodiversity and evolution of the investigated taxa. The relationship of the fauna to environmental parameters, such as water depth, sediment type, food availability and carbonate solubility, as well as species interrelationships, probably have shaped present-day biodiversity patterns as much as evolution. However, different taxa exhibit different large-scale biodiversity and biogeographic patterns. Moreover, there is rarely any clear relationship of biodiversity pattern with depth, latitude or environmental parameters, such as sediment composition or grain size. Similarities and differences between the SO biodiversity and biodiversity of global oceans are outlined. The high percentage (often more than 90%) of new species in almost all taxa, as well as the high degree of endemism of many groups, may reflect undersampling of the area, and it is likely to decrease as more information is gathered about SO deep-sea biodiversity by future expeditions. Indeed, among certain taxa such as the Foraminifera, close links at the species level are already apparent between deep Weddell Sea faunas and those from similar depths in the North Atlantic and Arctic. With regard to the vertical zonation from the shelf edge into deep water, biodiversity patterns among some taxa in the SO might differ from those in other deep-sea areas, due to the deep Antarctic shelf and the evolution of eurybathy in many species, as well as to deep-water production that can fuel the SO deep sea with freshly produced organic matter derived not only from phytoplankton, but also from ice algae.

A model‐based interpretation of low‐frequency changes in the carbon cycle during the last 120,000 years and its implications for the reconstruction of atmospheric Δ14C

A main caveat in the interpretation of observed changes in atmospheric Δ14C during the last 50,000 years is the unknown variability of the carbon cycle, which together with changes in the 14C production rates determines the 14C dynamics. A plausible scenario explaining glacial/interglacial dynamics seen in atmospheric CO2 and δ13C was proposed recently (Köhler et al., 2005a). A similar approach that expands its interpretation to the 14C cycle is an important step toward a deeper understanding of Δ14C variability. This approach is based on an ocean/atmosphere/biosphere box model of the global carbon cycle (BICYCLE) to reproduce low‐frequency changes in atmospheric CO2 as seen in Antarctic ice cores. The model is forced forward in time by various paleoclimatic records derived from ice and sediment cores. The simulation results of our proposed scenario match a compiled CO2 record from various ice cores during the last 120,000 years with high accuracy (r2 = 0.89). We analyze scenarios with different 14C production rates, which are either constant or based on 10Be measured in Greenland ice cores or the recent high‐resolution geomagnetic field reconstruction GLOPIS‐75 and compare them with the available Δ14C data covering the last 50,000 years. Our results suggest that during the last glacial cycle in general less than 110‰ of the increased atmospheric Δ14C is based on variations in the carbon cycle, while the largest part (5/6) of the variations has to be explained by other factors. Glacial atmospheric Δ14C larger than 700‰ cannot not be explained within our framework, neither through carbon cycle‐based changes nor through variable 14C production. Superimposed on these general trends might lie positive anomalies in atmospheric Δ14C of ∼50‰ caused by millennial‐scale variability of the northern deep water production during Heinrich events and Dansgaard/Oeschger climate fluctuations. According to our model, the dominant processes that increase glacial Δ14C are a reduced glacial ocean circulation (+∼40‰), a restricted glacial gas exchange between the atmosphere and the surface ocean through sea ice coverage (+∼20‰), and the enrichment of dissolved inorganic carbon with 14C in the surface waters through isotopic fractionation during higher glacial marine export production caused by iron fertilization (+∼10‰).

Comments: Deepwater Promise

The successful completion of an extended production test by Chevron, Statoil, and Devon on a well in the Lower Tertiary of the U.S. Gulf of Mexico (GOM) may prove to be a watershed event for the GOM and several operators, and could even usher in a new era of deepwater production. The much-anticipated test on the Jack #2 well on Walker Ridge Block 758 showed sustained flows of more than 6,000 BOPD. Operator Chevron, which has a 50% interest, and Statoil and Devon, each with a quarter share, plan an additional appraisal well next year. Jack, which was discovered in 2004, was one of the most closely watched GOM developments in recent memory because if development of the Lower Tertiary is feasible, it could open up a potentially prolific area to production. It is one of eight discoveries in the past 3 years in this GOM trend offshore Louisiana. Several analysts believe the area could produce as much as 500,000 BOPD within several years and hold as much as 15 billion bbl in reserves. Other estimates are more optimistic, predicting up to 800,000 BOPD of light, sweet crude and 1 billion cf/D day of natural gas coming from the reservoir by 2012. Chevron said that the Jack production test was the deepest successful well test in the GOM. Currently, there is no production from the Lower Tertiary, and Jack is one of several recent promising discoveries from this zone. Now the industry is finally beginning to get an idea of the extent of commercial hydrocarbons there. But output from the Lower Tertiary is not without significant hurdles. Mapping will be a challenge because of the thick salt layers, and wells and production facilities will be expensive. The Jack well is located in 7,000 ft of water and was drilled to a depth of more than 28,000 ft. Getting the production to the U.S. mainland—whether by pipeline or through the use of floating production systems—also presents issues. And, while the Jack test well met producers' expectations, overly optimistic expectations seem premature. Some of the industry's most promising and recent production developments are of increasing complexity. Hydro's Ormen Lange gas project in the North Sea, for example, is requiring complicated subsea installation and pipeline infrastructure. If the development of this trend confirms its expected potential, it will be another tribute to what upstream technology advances are making possible. Output from this deepwater frontier would not be possible without recent seismic advances as well as advances in rig technology. The news is certainly promising to several producers who hold additional leases nearby, including Chevron, Devon, Shell, Anadarko, and others. Devon said its Lower Tertiary acreage could more than double its reserves base of 2 billion BOE. Jack is one of four discoveries by Devon in the Lower Tertiary. The others are the Kaskida discovery made this year, the Malo prospect drilled in 2003, and Cascade—in which Devon doubled its working interest to 50% this summer—drilled in 2002. The Cascade prospect, scheduled for startup in 2009, will be the first deepwater Lower Tertiary field to come on line, according to the company. Devon, once a small U.S. independent, has grown rapidly during Chief Executive Officer Larry Nichols' tenure through a series of careful acquisitions and strategic drill-bit plays (see July 2006 JPT Q&A).

Late Quaternary palaeoceanography of the Circumpolar Deep Water from the South Tasman Rise

AbstractWe use sediment cores from the South Tasman Rise (STR) to reconstruct deep‐ water circulation in the southwest Pacific sector of the Southern Ocean. Sediment cores MD972106 (45° 09′ S, 146° 17′ E, 3310 m water depth) and GC34 (45° 06′ S, 147° 45′ E, 4002 m water depth) preserve records covering the last 160 k yr, with chronology controlled by calibrated accelerator mass spectrometry radiocarbon dates and benthic foraminiferal δ18O tied to SPECMAP. The STR benthic foraminiferal δ13C records provide new δ13C values for Southern Ocean deep water spanning the last 160 k yr at sites unlikely to be affected by variations in productivity. The records establish that glacial benthic foraminifera (Cibicidoides spp.) δ13C values are lower relative to interglacial values and are comparable to previous glacial benthic δ13C records in the Indian and Pacific sectors of the Southern Ocean. Comparisons of the benthic foraminiferal δ13C time series at the STR are made with the equatorial Pacific (V19‐30 and Site 846) and the equatorial Atlantic (GeoB1115). The similarity of benthic δ13C records at the STR to the equatorial Pacific suggest the Southern Ocean deep‐water mass closely tracked those of the deep Pacific, and the presence of a δ13C gradient between the STR and the equatorial Atlantic suggests there was continual production of northern source deep water over the past 160 k yr. Copyright © 2006 John Wiley & Sons, Ltd.

Analytical model for interfacial waves in vertical core flow

The vertical annular pipe flow of two immiscible liquids with very different viscosities provides an efficient and low cost method for producing heavy oils in vertical wells using water as a lubricant. The core flow pattern is becoming attractive in the current Brazilian deep water production scenario. Understanding interfacial phenomena present in this flow pattern is crucial for appropriate design of the production system. Assuming that in this axisymmetric flow there is no net force associated with interfacial tension, a differential equation governing the shape of the liquid–liquid interface is derived. An analytical solution is proposed for the prediction of the wave geometry, which depends only on pipe geometry, physical properties and flow rates of the fluids. The comparison between the model predictions and recent experimental data shows a reasonable agreement.

The Quest for Energy: Challenges of Deepwater Exploration

AbstractThis paper discusses the current keen attention on deepwater exploration and production for hydrocarbon energy sources. It analyses the factors and elements driving oil companies to engage enthusiastically in deepwater development activities. The features of such activities are discussed and the challenges faced by the oil companies to accommodate further expansion of activities in the field are outlined.

Ocean basins near the Scotia–Antarctic plate boundary: Influence of tectonics and paleoceanography on the Cenozoic deposits

The distribution of seismic units in deposits of the basins near the Antarctic–Scotia plate boundary is described based on the analysis of multichannel seismic reflection profiles. Five main seismic units are identified. The units are bounded by high-amplitude continuous reflectors, named a to d from top to bottom. The two older units are of different age and seismic facies in each basin and were generally deposited during active rifting and seafloor spreading. The three youngest units (3 to 1) exhibit, in contrast, rather similar seismic facies and can be correlated at a regional scale. The deposits are types of contourite drift that resulted from the interplay between the northeastward flow of Weddell Sea Bottom Water (WSBW) and the complex bathymetry in the northern Weddell Sea, and from the influence of the Antarctic Circumpolar Current and the WSBW in the Scotia Sea. A major paleoceanographic event was recorded by Reflector c, during the Middle Miocene, which represents the connection between the Scotia Sea and the Weddell Sea after the opening of Jane Basin. Unit 3 (tentatively dated ∼Middle to Late Miocene) shows the initial incursions of the WSBW into the Scotia Sea, which influenced a northward progradational pattern, in contrast to the underlying deposits. The age attributed to Reflector b is coincident with the end of spreading at the West Scotia Ridge (∼6.4 Ma). Unit 2 (dated ∼Late Miocene to Early Pliocene) includes abundant high-energy, sheeted deposits in the northern Weddell Sea, which may reflect a higher production of WSBW as a result of the advance of the West Antarctic ice-sheet onto the continental shelf. Reflector a represents the last major regional paleoceanographic change. The timing of this event (∼3.5–3.8 Ma) coincides with the end of spreading at the Phoenix–Antarctic Ridge, but may be also correlated with global events such as initiation of the permanent Northern Hemisphere ice-sheet and a major sea level drop. Unit 1 (dated ∼Late Pliocene to Recent) is characterized by abundant chaotic, high-energy sheeted deposits, in addition to a variety of contourites, which suggest intensified deep-water production. Units 1 and 2 show, in addition, a cyclic pattern, more abundant wavy deposits and the development of internal unconformities, all of which attest to alternating periods of increased bottom current energy.

Overview: Deepwater Exploration and Production (June 2006)

Deepwater oil and gas projects are some of the most challenging of human endeavors. The sheer size of many of these efforts—and the impressive new technologies used—is truly amazing. Deepwater projects also entail great risk, however, and things sometimes do go wrong. Of course, things go wrong on all types of projects, but the deepwater environment itself and the large-scale nature of many projects exacerbate the severity of any problem. Costs can increase to many times the budget, the details associated with implementing new technology can be overwhelming, and schedules easily can slip enough to jeopardize the commercial success of the project. Some problems are related to project decisions that are made to maintain schedule before all of the needed facts are available. On a complex project, decisions are made that, in retrospect, are clearly wrong. Other problems arise simply as a result of mistakes made by the project management or technical teams. To be successful, the project team must be willing to recognize mistakes as early as possible and take corrective action. Knowledge of how mistakes were addressed on previous projects, both successfully and unsuccessfully, can be invaluable in selecting an appropriate corrective action. Examining lessons learned from previous projects provides one of the most important methods for improving project execution. Barry LePatner, an attorney testifying before a U.S. House of Representatives Science and Technology Committee on disclosure of information from building failures, made the following observation: "Good judgment is usually the result of experience. And experience is frequently the result of bad judgment. But to learn from the experience of others requires those who have the experience to share the knowledge with those who follow." The sharing of project-management lessons learned on deepwater projects, however, is a relatively recent development. Project management is as important to the success of deepwater projects as technology. The continued sharing of project-management lessons learned would help project teams meet the myriad nontechnical challenges associated with deepwater projects. Deepwater Exploration and Production additional reading available at the OTC Library: www.otcnet.org OTC 17971 "Albacora Leste Deepwater Field: Improvements on Well Construction," by E. de Melo Sanches, Petrobras, et al. OTC 17806 "Combined Effect of Flowline Walking and Riser Dynamic Loads on HP/HT Flowline Design," by M.S. Brunner, Technip U.S.A., et al. OTC 18311 "K2 Topside Facilities—Design Challenges," by F. Colbert, OFD Engineering LLC, et al. OTC 17655 "The Significance of Gas Hydrate as a Geohazard in Gulf of Mexico Exploration and Production," by M.A. Smith, U.S. Dept. of the Interior, Minerals Management Service, et al.

Numerical study of the meridional overturning circulation with “mixing hotspots” in the Pacific Ocean

Using an idealized ocean general circulation model, we examine the effect of “mixing hotspots” (localized regions of intense diapycnal mixing) predicted based on internal wave-wave interaction theory (Hibiya et al., 2006) on the meridional overturning circulation of the Pacific Ocean. Although the assumed diapycnal diffusivity in the mixing hotspots is a little larger than the predicted value, the upwelling in the mixing hotspots is not sufficient to balance the deep-water production; out of 17 Sv of the downwelled water along the southern boundary, only 9.2 Sv is found to upwell in the mixing hotspots. The imbalance as much as 7.8 Sv is compensated by entrainment into the surface mixed layer in the vicinity of the downwelling region. As a result, the northward transport of the deep water crossing the equator is limited to 5.5 Sv, much less than estimated from previous current meter moorings and hydrographic surveys. One plausible explanation for this is that the magnitude of the meridional overturning circulation of the Pacific Ocean has been overestimated by these observations. We raise doubts about the validity of the previous ocean general circulation models where diapycnal diffusivity is assigned ad hoc to attain the current magnitude suggested from current meter moorings and hydrographic surveys.

Contribution of giant icebergs to the Southern Ocean freshwater flux

In the period 1979–2003 the mass of “giant” icebergs (icebergs larger than 18.5 km in length) calving from Antarctica averaged 1089 ± 300 Gt yr−1 of ice, under half the snow accumulation over the continent given by the Intergovernmental Panel on Climate Change (2246 ± 86 Gt yr−1). Here we combine a database of iceberg tracks from the National Ice Center and a model of iceberg thermodynamics in order to estimate the amount and distribution of meltwater attributable to giant icebergs. By comparing with published modeled meltwater distribution for smaller bergs we show that giant icebergs have a different melting pattern: An estimated 35% of giant icebergs' mass is exported north of 63°S versus 3% for smaller bergs, although giant bergs spend more of the earlier part of their history nearer to the coast. We combine both estimates to produce the first iceberg meltwater map that takes into account giant icebergs. The average meltwater input is shown to exceed precipitation minus evaporation (P − E) in certain areas and is a nonnegligible term in the balance of freshwater fluxes in the Southern Ocean. The calving of giant icebergs is, however, episodic; this might have implications for their impact on the freshwater budget of the ocean. It is estimated that over the period 1987–2003 the meltwater flux in the Weddell and Ross seas has varied by at least 15,000 m3 s−1 over a month. Because of the potential sensitivity of the production of deep waters to abrupt changes in the freshwater budget, variations in iceberg melt rates of this magnitude might be climatologically significant.

Evolution of Atlantic thermohaline circulation: Early Oligocene onset of deep-water production in the North Atlantic

The flow of deep-water masses is a key component of heat transport in the modern climate system, yet the role of deep-ocean heat transport during periods of extreme warmth is poorly understood. The present mode of meridional overturning circulation is characterized by deep-water formation in both the North Atlantic and the Southern Ocean. However, a different mode of meridional overturning circulation operated during the extreme greenhouse warmth of the early Cenozoic, during which time the Southern Ocean was the dominant region of deep-water formation. The combination of general global cooling and tectonic evolution of the Atlantic basins over the past ∼55 m.y. ultimately led to the development of a mode of overturning circulation characterized by both Southern Ocean and North Atlantic deep-water sources. The change in deep-water circulation mode may, in turn, have affected global climate; however, unraveling the causes and consequences of this transition requires a better understanding of the timing of the transition. New Nd isotope data from the southeastern Atlantic Ocean indicate that the initial transition to a bipolar mode of deep-water circulation occurred in the early Oligocene, ca. 33 Ma. The likely cause of significant deep-water production in the North Atlantic was tectonic deepening of the sill separating the Greenland-Norwegian Sea from the North Atlantic.

HYDRATES—A CHALLENGE IN FLOW ASSURANCE FOR OIL AND GAS PRODUCTION IN DEEP AND ULTRA-DEEP WATER

Offshore exploration and production is going to deep and ultra deep waters, driven by the depletion of continental shelf reserves and the high demand for hydrocarbons. This move requires the continued extension of existing technologies and the development of new technologies that will make the investment economically viable. Innovative flow assurance technology is needed to support ultra deepwater production, particularly within the concept of platform free fields where there is a need to minimise interventions.Hydrates present one of the major challenges in flow assurance. Deep and ultra deep water operations together with long tiebacks present the ideal conditions for the formation of hydrates which can result in pipeline blockage and serious operational and safety concerns. Methods to combat hydrates range between control and management. One main technique has been to produce the hydrocarbons outside of the thermodynamic stability domain of hydrates. This is achieved by keeping the temperature of the hydrocarbon above the stability temperature of hydrates by insulating the pipe line, or by introducing heat to the hydrocarbon. Another efficient way of combating hydrates has been to shift the hydrate phase boundary to lower temperatures by using chemicals like methanol and mono ethylene glycol (MEO) which are known as thermodynamic inhibitors. Within the last decade a new generation of hydrate inhibitors called low dosage hydrate inhibitors (LDHI) has been introduced. One type of these LDHI are kinetic hydrate inhibitors (KHI) that, when used in small concentrations, slow down hydrate growth by increasing the induction time for their formation and preventing the start of the rapid growth stage. Another approach to managing hydrates has been to allow them to form in a controlled manner and transport the hydrate-hydrocarbon slurry in the production pipe. In this paper we describe the various approaches used to combat hydrates to ensure flow assurance and we discuss the cons and pros of every approach and the technology gaps.

Statistical response predictions for a nonlinearly moored large volume structure in random seas

The challenge to calculate the response statistics of nonlinear, compliant offshore structures subjected to a random seaway is still substantial. In this paper the results are presented of a renewed effort to use the method of numerical path integration for this purpose. In particular, the goal is to calculate the response statistics of a nonlinearly moored large volume floater designed for use in oil production in deep waters. Specific emphasis has been placed on the modelling of nonlinear wave loads in addition to the nonlinear mooring characteristics. The results calculated for the response statistics are compared with the results obtained by Monte Carlo simulation, and the agreement is found to be very good.

Arctic Ocean change heralds North Atlantic freshening

A large pool of freshwater formed of ice and runoff is hosted by the Arctic Ocean. It exits through the Canadian Archipelago and Fram Strait to enter the North Atlantic deep water production regions. Using a numerical model and observations we trace a strong freshwater release to subpolar waters in the mid‐1990s. In contrast to the ice export driven 1970's ‘Great Salinity Anomaly’ its source was a large additional liquid freshwater release from the Arctic Ocean. In fact it was a consequence of a change of the Arctic Ocean's thermohaline structure in response to the very intense North Atlantic Oscillation in the early 1990s. Our results show a strong link of large‐scale Arctic Ocean changes with the freshwater flux to subpolar waters.

Mechanisms for millennial‐scale global synchronization during the last glacial period

Global climate during the last glacial period was punctuated by abrupt warmings and occasional pulses of freshwater into the North Atlantic that disrupted deepwater production. These massive freshwater pulses known as Heinrich events arose, in part, from instabilities within the Laurentide ice sheet. Paleoevidence from the North Atlantic suggests that these events altered the production of deep water and changed downstream climate throughout the Northern Hemisphere. In the tropical western Pacific sea, surface temperatures and salinity varied together with ocean and climate changes at high latitudes. Here we present results from coupled modeling experiments that shed light on a possible dynamical link between the North Atlantic Ocean and the western tropical Pacific. This link involves a global oceanic standing wave pattern brought about by millennial‐scale glacial density variations in the North Atlantic, atmospheric teleconnections triggered by meridional sea surface temperature gradients, and local air‐sea interactions. Furthermore, our modeling results are compared with hydrological records from the Cariaco basin, the Indian Ocean, the Sulu Sea, and northern Australia.

Comments: Storm on the Horizon

It is already a very active hurricane season in the Atlantic. Seven tropical storms, including two major hurricanes, occurred in June and July. That is the most major Atlantic storms this early in the hurricane “season”—which runs from June to November—since 1851. The U.S. Natl. Weather Service now predicts 18–21 tropical storms this year, with nine to 11 becoming hurricanes, including five to seven major hurricanes. That would be one of the most active Atlantic hurricane seasons on record and the ninth above-normal Atlantic hurricane season in the past 11 years. With global oil supplies tight and the oil market seemingly on edge, any storm that disrupts even short-term production would cause prices to spike. And with deepwater production from the Gulf of Mexico (GOM) becoming a major source of supply for the U.S., and Mexico also venturing farther out into the gulf, the issue of hurricanes and how to withstand them has become a major topic of concern for producers. What really got the industry’s attention was last September’s Hurricane Ivan in the GOM. That storm seriously damaged 31 platforms, destroyed several more, and disrupted more than 10% of GOM output for 4 months. It shut down most of the production in the eastern portion of the gulf and damaged pipelines and platforms along a wide swath, but there was no loss of life, and no major pollution occurred. High waves destroyed six platforms, and a mudslide destroyed another. Then in July, Hurricane Dennis affected BP’s Thunder Horse platform in the GOM, the world’s largest semisubmersible platform. After evacuating from the storm, workers returned to find the platform listing at a 30-degree angle, although it has since been righted. Dennis was classified as a strong Category 3 storm, with winds of 120 miles/hr. Thunder Horse, designed to process up to 250,000 BOPD and 200 MMcf/D of gas, was expected to come on line later this year. That timing is now in doubt. It is the largest field in the U.S. GOM, with recoverable reserves of 1 billion bbl. During a panel session at this year’s Offshore Technology Conference, representatives from the U.S. Minerals Management Service (MMS) said it was particularly concerned about the anchoring of drilling rigs on production platforms, mobile rigs that had broken off mooring, and the pipeline damage. The MMS recently authorized six studies that will examine the impact that Hurricane Ivan had on oil and gas structures and will recommend how to make offshore pipelines and platforms more resistant to storm damage. Included in the reports will be an assessment of the effectiveness of current design standards and pollution-prevention measures. MMS awarded more than U.S. $600,000 to Texas A&M U., Offshore Risk and Technology Consulting, Det Norske Veritas, Energo Engineering, and William Lettis and Assocs. to study, among other things, hardware on offshore floating platforms, mooring standards, pipeline damage, and the occurrence and effect of mudflows and mudslides. The studies are expected to be completed over the next 14 months. Some changes already have been made after experiences with last year’s and this year’s storms. Companies that have platforms shut down because of storms now must make daily production-loss reports to the MMS. Rigs and platforms now must be equipped with glob-al positioning devices so that they can be quickly recovered after a hurricane. And the industry is now securing bolting mechanisms and clamps on drilling units before evacuating rigs. Of course, hurricanes in the Atlantic and their impact on the industry are nothing new. A hurricane crippled Mexico’s production from the Bay of Campeche in the early 1990s. SPE’s eLibrary has technical papers on hurricane case studies and modeling going back 3 decades. The industry’s first experience with hurricanes in the gulf occurred in the 1930s, when a trestle that extended a mile from shore south of Port Arthur, Texas, with drilling rigs at the end of the line was destroyed by a small hurricane. That type of structure had worked well for offshore drilling in California, but it quickly became clear that it would not work in the GOM. From then on, engineers have struggled with building offshore structures that could withstand the powerful winds and waves spawned by fierce storms.

Overview: Offshore Completions (August 2005)

Last year, in this space, I commented on innovations being implemented on recent offshore completion projects and how offshore completion practices have undergone major changes. Our industry, regarding offshore developments, apparently has an unlimited ability to amaze the world with new advances. Projects that were considered not feasible 5 years ago now are being implemented. Driven by various reasons, including depletion of conventional reserves and increasing oil prices, oil and gas production in deep water became customary in many regions around the world, and it was not a surprise that, during the 2005 Offshore Technology Conference, oil companies started to reveal plans aiming at production of fields under 3000 m of water. Use of intelligent-well completions is spreading globally, not only for large deepwater projects, but also for small offshore discoveries where its use in subsea satellite wells may bring profitability to an otherwise uneconomical project. Smart systems, with remotely operated valves, allow operators to control various producing zones, shutting down those not responding as expected without expensive well interventions. All of that can be achieved while data for each independent zone are simultaneously acquired and recorded. Developing fields that present complex geology and deep reservoirs that have high pressures and temperatures still present challenges for the industry, mainly when unconventional-trajectory wells are used. Some of the issues being investigated involve completion of long horizontal sections in unconsolidated reservoirs; flow assurance, mainly for deepwater conditions; and subsea processing, including gas compression and gas/liquid and oil/water separation. Some of these challenges are addressed well in the papers featured in this issue. Available from the SPE eLibrary: www.spe.org SPE 90552 - “Gravel Packing Deepwater Long Horizontal Wells Under Low Fracture Gradient,” by Chen, Zhongming, SPE, BJ Services, et al. Available from the OTC Library: www.otcnet.org OTC 17399 - “Subsea Gas Compression—Challenges and Solutions,” by Fantoft, R., FMC Kongsberg Subsea A/S OTC 17397 - “Hybrid Riser Towers From an Operator’s Perspective,” by Sworn, A., BP plc