After an operator confirmed wellbore integrity failure in a well located on a small platform, a coiled tubing (CT) catenary intervention was urgently required. However, the production facilities of the platform were not authorized to operate, which represented an impediment to receive returns from the wellbore. This paper documents the analysis and implementation of nonconventional flowback methods and the actions taken to perform the intervention using a state-of-the-art fly-by-wire CT catenary package in a setup that had never used before in this field.
After a shut-in period, the subject well faced integrity issues that could end in an uncontrolled situation. To remediate this situation, milling and plug-setting runs were designed using a catenary system with a fly-by-wire CT unit set for first time completely on the vessel and leaving only the injector head on the platform. To address the flowback limitation, technical and economical assessments were performed on three options: using slope barges to receive fluids in storage tanks, setting conventional flowback equipment on board the catenary vessel, or using the gas injection pipeline available on the platform.
After analyzing each alternative, the options to use slope barges and flowback equipment on the vessel were discarded after confirming that they represented an additional risk and generated higher costs for their implementation. The use of the gas injection pipeline involved the modification of many resources on land and at the offshore facilities, and a detailed plan was needed to utilize the lines in a different way from their initial design. Additionally, weather conditions played a major role during the job execution. Consequently, a special focus was placed on elaborating contingency plans to address emergencies during the operation taking into account that the method implied handling hydrocarbons at surface under uncommon situations. The coordination and collaboration in the operation enabled the operator to achieve the expected results, recovering the wellbore integrity in a cost-effective way, while also eliminating the exposure of additional vessels or sophisticated equipment on location.
The paper presents the large amount of information that was amassed during the implementation of the solution, which could be used by other locations facing similar conditions where conventional production facilities cannot be used during well interventions. The document also includes contingency plans for every stage of the project, safety measurements, lessons learned, and details of the modifications done to the gas injection system and the CT equipment.
Gangway equipped: offshore support vessels, intervention vessels, construction vessels, and other monohull vessels, capable of providing gangway access to offshore facilities in exposed sea areas has great potential. It is playing an evolving important role in making new marginal yield field development economical, reducing exposure to risk, and extending the life of the existing oil and gas infrastructure. Otherwise known as Walk to Work (W2W), this marine manning approach for offshore facilities can be used on a regular, fixed term, ad-hoc or exceptional circumstance basis. It is capable of providing significant benefits over existing provisions including: improved safety, increased workforce productivity, greater manning flexibility, and reduced lifecycle costs. The W2W vessel can range from relatively small, fast workboats, to large semi-submersible'flotels' stationed alongside fixed platforms. Within this range, it is the mono-hull vessel where there is the greatest opportunity for the oil and gas industry to realise significant (currently unexploited) gain. Depending on the capability of the chosen vessel, a W2W solution may offer: gangway transfers, hotel, hospital, helicopter, rescue and recovery, subsea and splash zone inspection, cargo, crane, fabrication and other facilities.
Plug and Abandonment (P&A) can easily contribute with 25% of the total costs of drilling exploration wells offshore Norway. Cost efficient P&A technology is therefore necessary to reduce cost of exploration drilling. In this paper, qualified technology for cutting and retrieval of wellheads using a separate vessel is described in detail. It is shown how to use this technology to significantly reduce the total costs of exploration drilling. The technology has now been used on several abandonment operations on the Norwegian continental shelf.
In the paper it is presented through examples how efficient P&A operations are run using a dedicated vessel to perform parts of the wellhead cutting and retrieval operation earlier conducted with the drilling rig. Examples illustrate how the different wells are permanently plugged back to maintain all barrier requirements before the drilling rigs leave the wells with wellheads in place. During a later wellhead removal campaign a dedicated vessel arrives cutting the casings underneath the sea bed and finally removes the wellheads. It is shown that removal of more than two wellheads in a campaign is necessary to make this type of operation cost efficient.
By transferring activities like Plug and Abandonment (P&A) and anchor handling from rig to dedicated vessels, the cost of drilling operations will be reduced and drilling production will be increased (Sørheim et al., 2011). The objective of transferring these activities to the dedicated vessels is to maintain the drilling rig activity at their core functions, which are drilling and completing wells. For example, in offshore drilling operations it is generally more cost effective to pre-set anchors prior to arrival of drilling rigs than to let the rig be an active part in anchor handling (Saasen et al., 2010). Similarly it can be efficient to pre-set conductors prior to rig arrival. As mentioned, permanent P&A is also an operation where activities can successfully be moved from rigs to dedicated vessels. In addition to the economical benefits of moving activities to dedicated vessels, there is a significant Health, Safety and Environment (HSE) benefit. These transferred activities are now conducted by specialised personnel on dedicated vessels. On the rigs these activities will be parallel to other rig activities and thereby represent a slightly higher HSE risk.
Going and Haughton (2001) presented tools for casing string recovery including casing cutter, a hydraulic casing spear and a combined marine swivel/hanger seal extractor have been presented earlier. This system has successfully been used on drilling rigs to remove casing strings and wellheads. P&A without the use of drilling rigs is currently a routine operation on land wells. See for example Tettero et al. (2004). These techniques however, are not straightforward in offshore operations.
P&A of offshore exploration wells represents a significant part of the drilling cost especially for production wells. Normally these operations are conducted by removing completion equipment followed by placement of a series of cement plugs. This application of cement plugs is described by for example Liversidge et al. (2006). Also, while drilling exploration wells, the P&A operation is a significant cost. Therefore, a method using a concentrated sand slurry for P&A of the reservoir has been applied to minimise the time to wait for the cement to cure (Saasen et al., 2011). In the following it is shown how parts of the P&A operation successfully have been transferred from the rig to a dedicated vessel and thereby reduced rig time on non-drilling activities.
Trans-Tasman Resources Limited (TTR) was established in September 2007 in New Zealand to explore, assess and develop the off shore titano-magnetite iron sand deposits, located off the west coast of the North Island of New Zealand.
TTR holds exploration permit(s) and a prospecting license granting exclusive mineral rights over 9633 km2 of seabed, within New Zealand's territorial and Exclusive Economic Zone (EEZ) waters. Subsequent to a large airborne magnetic survey, TTR has undertaken a series of shallow and deep drilling campaigns which have defined an initial JORC1 mineral resource. This JORC compliant mineral resource was defined by Golders Associates on the basis of drilling campaigns that were performed using in house designed and operated drilling units, the first of its kind in the world.
TTR is developing innovative solutions for all aspects of its exploration and feasibility studies. In relation to exploration, TTR are competing in an environment which has offshore contractors and equipment focused on the petroleum industry, therefore it has been essential that TTR remain innovative to ensure cost effectiveness, fit for purpose and industry standards (JORC) are paramount. Exploration to date has enabled TTR to estimate an offshore titano-magnetite iron sand resource, using low cost marine reverse circulatory drilling units developed specifically for this purpose (patent pending) in conjunction with other exploration techniques.
The purpose of this paper will be to discuss some of the main challenges in the exploration and the subsequent engineering studies used in the feasibility studies for the development one of the world's first large off shore mineral resource of iron ore. The key strategic advantage of the envisaged off shore wet mining operation would be its much lower capital cost compared to land based operations, as no deep sea port or heavy gauge rail is required.
During a period spanning 2009–2010, TOTAL E&P Congo undertook an integrated acquisition, processing and interpretation project. As this project required accurate imaging of both post-salt and pre-salt structures, a broad bandwidth seismic solution was required. The imaging requirements led to the first 3D dual sensor acquisition in the Gulf of Guinea which contributed to a step change in seismic quality for this area. After efficient and safe acquisition operations, an ultra-fast track processing route was adopted in conjunction with more conventional processing enabling phased refinement of an upcoming exploration drilling campaign.
As the world's population grows and economies develop, the demand for energy will continue to grow significantly. This increased demand is also being underpinned by the desire for cleaner source of energy to minimize impact on the environment. The International Energy Agency and many others predict that the world's total energy demand will grow by about 35% in 2030 from today's level. Crude Oil and Natural gas are estimated to account for nearly 60% of total energy supply through 2030 for a number of reasons. The growing attractiveness of global Natural gas development also supports the general consensus and forecast that Natural gas will overtake oil towards the middle of the century as a primary energy source. Natural gas is also being used in a variety of processes as feedstock, fuel, etc. Its contribution to world energy resources is growing leading to the concept that it is a bridge to the ultimate hydrogen economy. The flexibility brought about by growing importance of liquefied natural gas, LNG, is also changing the dynamics of the natural gas supply and demand equilibrium. The massive growth in global LNG demand and the challenging supply constraints are putting pressure on the industry to think of more innovative ways to harness and monetize stranded gas fields in a cost-effective and creative manner. Some schools of thought believe that as much as 40% or more of the total global gas reserves is stranded and needs to be brought to market creatively. Such stranded gas resources, found in deep offshore acreages and such remote locations are typically isolated from onshore processing facilities and may not be profitably developed by conventional means. This creates the niche application for the Floating LNG technology as creative way of monetizing the resources. The majority of the world's stranded gas reserves are located in the CIS (30%) and the Middle East (25%). Africa was third, with 16% of the reserves, and was followed by the Far East (13%), Latin America (13%), Alaska (5%) and Australasia (3%). The top-five countries for stranded gas are Russia, Iran, Nigeria, Saudi Arabia, and the Alaskan North Slope in the U.S. This paper seeks to identify and emphasize the role and contribution of floating LNG as a more effective way of having access to and monetizing stranded reserves and associated gas, in an environmentally responsible manner safely. This paper also reviews the current status of FLNG projects, to highlight the technical and commercial obstacles that still confront them, and offer insight into how these obstacles might be overcome.
Keywords: Floating LNG, Stranded Reserves, Natural Gas, Liquefaction
Description. Low salinity water floods and chemical enhanced oil recovery (CEOR) injection (Alkali, Surfactant and Polymer) are two technologies which have been applied onshore but are now being studied for use in new and existing offshore field developments. Their application offshore introduces several issues, which can significantly affect the technical feasibility and commercial viability of the project.
1. For "Greenfield?? and "Brownfield" projects the most suitable location of the CEOR facilities to minimize additional field infrastructure costs,
2. For "Brownfield?? projects the most suitable location of the CEOR facilities to optimize logistics, maximize safety and minimize the impact on ongoing production operations, during both the construction and operations phases,
3. The most suitable time in the field development schedule to install the CEOR facilities to maximize the availability of reservoir data and to minimize the initial platform costs.
The results presented in this paper are generic but they provide a basis for further study of the application of a dedicated desalination / CEOR vessel using specific field information. A work sheet has been provided in the paper identifying the most likely design concept(s) of a dedicated CEOR unit for a range of different field location parameters.
Results, Observations, and Conclusions.
In many cases the lowest risk and most cost efficient design is to locate the desalination / CEOR facilities on a separate vessel. This paper addresses the comparison of these issues in a qualitative manner for different design scenarios. The concept selection comparison is based upon engineering studies and typical offshore industry cost metrics.
This paper presents a basis for considering a dedicated CEOR vessel for offshore projects. This is a novel concept and by initiating further detailed analysis for specific field developments this paper could provide the impetus for the recovery of a significant amount of additional offshore field reserves.
The application of Enhanced Oil Recovery (EOR) technologies such as low salinity water floods and Alkali, Surfactant, Polymer (ASP) water floods, to oil field developments is not new to the oil industry but the application of these technologies to offshore fields is new to the oil industry. . Reduction in chemical costs as well as increased knowledge of the reservoir through 3D seismic data and improved computer modeling has made the application of EOR technologies offshore economic in many cases. These technology improvements, as well as the difficulty in accessing new exploration areas and the political drivers to maximize national resources, has made the application of EOR to the relatively large offshore fields, a higher priority within the major, national and independent oil companies.
González, M. Míguez (Integrated Group for Engineering Research, University of A Coruña) | Peña, F. Lopez (Integrated Group for Engineering Research, University of A Coruña) | Casás, V.Díaz (Integrated Group for Engineering Research, University of A Coruña) | Galeazzi, R. (DTU Electrical Engineering, Technical University of Denmark) | Blanke, M. (DTU Electrical Engineering, Technical University of Denmark, Centre for Ships and Ocean Structures, Norwegian University of Science and Technology)
Kozin, V.M. (Institute of Machine Science and Metallurgy, Far East of the Russian Academy of Sciences Amur Humanitarian-Pedagogical State University) | Zemlyak, V.L. (Institute of Machine Science and Metallurgy, Far East of the Russian Academy of Sciences Amur Humanitarian-Pedagogical State University)