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Collaborating Authors
Sonangol
Integrated Approach to Leak Detection Using High-Definition Electromagnetic Technology, Production Logging and Ultrasonic Logs – A Case Study
Adedamola, Adesoji (Halliburton) | Chakraborty, Diptaroop (Halliburton) | Sedlacek, Ariel (Halliburton) | Tambwe, Tshissola (Sonangol) | Hay, Neil (Sonangol) | Dode, Salomao (Sonangol) | Cruz, Abel (Sonangol) | Rodrigues, Jose (Sonangol) | Nzau, Jose (Sonangol) | Cunha, Adriano (Sonangol) | Mavuba, Olivio (Sonangol) | Andrade, Domingos (Sonangol)
Abstract The importance of well integrity cannot be over-emphasized due to the environmental and economic implications of the associated challenges. The integrity of oil and gas wells is of utmost significance throughout their lifecycle from drilling to abandonment. Various subsurface events could lead to the deterioration of the integrity of wells over time. Corrosion of the tubulars is a major well integrity challenge in the oil and gas industry as it causes metal losses and this in turn could lead to pressure communication/fluid leakage across damaged zones. Hence, a comprehensive understanding of the source of leaks becomes very important in order to plan appropriate remedial actions and also to evaluate the general tubular conditions to avoid future well integrity issues. To perform such investigations, more often the companies prefer to use solutions without retrieving any completion thus making it essential to have advanced technologies that work in through-tubing logging scenarios. This work focuses on an integrated approach in the successful diagnosis of tubular leaks by combining high-definition electromagnetic technology with production log data and ultrasonic logs. The first part of the well integrity assessment was carried out without having to pull any completions as the electromagnetic tool was deployed through the tubing. The capability of the high-definition electromagnetic technology in resolving metal loss in up to five concentric strings is the first critical piece of the solution. Later production logs and ultrasonic logs were run and integrated with the electromagnetic data to provide a complete understanding of the identified leak zones. For the presented case study, the primary objective of the well integrity evaluation was to determine the leak point between the 9-5/8″ and 13-3/8″ casings by running through the existing completions, as pressure communication was observed on surface between the respective annuli. From the analysis of the acquired data, significant metal loss was observed in the second string (9-5/8″ pipe) and this was corroborated later by the ultrasonic data and production logs. In addition, considerable metal loss was observed in the third string of pipe (13-3/8″ pipe) near the 20″ casing shoe (4th string) with a corresponding diagnosis observed from the acquired temperature log. The successful determination of the leak points has helped the operator plan the appropriate remedial actions to fix the annuli in communication and also the unanticipated 13-3/8″ pipe damage.
- Well Drilling > Casing and Cementing > Casing design (1.00)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Abstract This paper will describe the CLOV deepwater mega-project in Block 17, offshore Angola. This major development encompasses four separate oil and gas accumulations in waters up to 1,400 metres and aims to recover 505 million barrels of both light and heavier oil plus associated gas in sufficient quantities that will require an export solution to shore for inclusion in the Angola LNG project. CLOV - which comprises the Cravo, Lirio, Orquidea and Violeta fields - is the fourth large-scale development in this block within the Angolan offshore sector executed by Total. Like the previous three, it is based around floating production storage and offloading (FPSO) vessel and an extensive subsea production system. The execution of CLOV benefited from lessons learned on the three earlier projects - Girassol, Dalia and Pazflor. This resulted in a successful project measured on technical and schedule parameters as well as cost control. This project presents significant challenges in development including the drilling of 34 development wells requiring two drill ships and the equivalent of almost 2,500 drilling days. The heavier oil reservoirs of Orquidea and Violeta need pressure and flow support and require the use of both a large water injection scheme (six subsea water injectors) making use of produced water from the FPSO and the installation of a seabed multiphase pumping system based on helico-axial pumps. The production wells have a range of completion designs and sand control methods. The FPSO - a purpose-built unit of 305m by 61m with topside of 37,000 tonnes net dry weight - employs an all-electric power system with variable speed drives. It also makes use of the ‘wash tank’ technique for oil-water separation. Both are firsts on projects developed by Total. The SURF (subsea umbilical, risers and flowlines) element of the project required three hybrid riser towers, nearly 100 kilometres of infield flowlines plus a 32km gas export line.
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Lifecycle > Disposal/Injection (0.35)
- Africa > Angola > South Atlantic Ocean > Lower Congo Basin > Block 17 > CLOV Fields > Orquidea Field > Orquidea-1 Well (0.99)
- Africa > Angola > South Atlantic Ocean > Lower Congo Basin > Block 17 > Violeta Field (0.94)
- Africa > Angola > South Atlantic Ocean > Lower Congo Basin > Block 17 > Lirio Field (0.94)
- Africa > Angola > South Atlantic Ocean > Lower Congo Basin > Block 17 > Cravo Field (0.94)
Abstract Local content was fundamental to Total E&P Angola's development philosophy for the CLOV mega-project, offshore Angola. The aim - to allow CLOV to provide with a lasting legacy in terms of human and facilities resources - was to achieve 10 million man-hours of local activity in Angola at first oil - a tenfold increase from Total's first deepwater development at Girassol - and the fabrication of 64,000 tonnes of structures in five domestic construction yards. Based on Total E&P Angola's policy of sustainable development, a plan was devised and executed that included specific health, safety, environmental and quality requirements and ethical standards, all in accordance with Angola's socio-economic and cultural characteristics. Local content challenges were identified at early stage of the project. It allowed the development of a sound strategy based on selection, management and execution. This resulted in the upgrades of three of the five fabrication yards which were implemented in a cost-effective and timely fashion to meet overall project cost and schedules. It was of paramount importance that if these yards were to perform essential work, they had to be manned with a skilled local workforce. Therefore, training was another key area of development for both the project team and contractors.
- Africa > Angola (1.00)
- North America > United States > Texas (0.29)
Pre-Salt Hydrocarbon Prospectivity in the Kwanza and Benguela Basins of Offshore Angola
Greenhalgh, Jennifer (Petroleum Geo-Services) | Borsato, Ron (Petroleum Geo-Services) | Mathew, Frances (Petroleum Geo-Services) | Duncan-Jones, George (Petroleum Geo-Services) | Primenta, Idima (Sonangol) | da Silva, Jandira Marques (Sonangol) | da Silva, Luis Narciso (Geotec)
Summary The frontier offshore basins of Angola hold tremendous potential for hydrocarbons in the Pre-Salt section. The Angolan basins have similarities with the Pre-Salt of the Brazilian margin which abutted the Angola offshore area prior to opening of the South Atlantic. Traps were formed during rift phases and include horsts and tilted fault blocks. Depth-migrated dual-sensor streamer seismic improves the imaging of syn-rift structures, which now allows the identification and mapping of prospects in underexplored acreage.
- Africa > Angola > South Atlantic Ocean (0.54)
- Africa > Angola > Benguela Province > Benguela (0.44)
- Geophysics > Seismic Surveying > Seismic Processing (0.70)
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (0.51)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Block BM-S-11 > Tupi Field > Lula Formation (0.99)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Block BM-S-11 > Tupi Field > Guaratiba Formation (0.99)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Block BM-S-11 > Tupi Field > Cernambi Formation (0.99)
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Abstract Pazflor project provides an opportunity to introduce major technologyinnovations in the Angolan oil industry and to pursue the development of thecountry's economic and industrial fabric. With PAZFLOR a new giant has been added to the portfolio of Angolan offshoreproducing facilities. When it reaches its plateau, 220 000 bbl/j will be addedto the production of the country. This will participate to a large extent inthe expected increase of Angolan production from 1.7 M bbl/d in 2011 to morethan 2 M bbl/d in 2012. Beyond this daily production increase, PAZFLOR is alsothe mean of access to about 600 million additional barrels that Angola needs tomeet its development ambitions. The position of Angola among oil producingcountries will thus be strengthened. Ten years after Girassol, the first deep offshore development in the countryand on the same golden block 17, PAZFLOR presents one more huge technologicalworld first with its three large scale oil subsea separation and pumping unitsinstalled at 800m WD, and its facilities capable to process 2 types of oil verydifferent in nature, its world's largest FPSO ever built and its 600 km subseaproduction network. Such an achievement has been made possible thanks to a strong cooperationbetween Sonangol and Total. It validates the strategy chosen by Angola so farto develop its reserves and proves, again, the ability of SONANGOL in workingwith major oil companies like TOTAL to build on each party's knowhow andcompetences. This experience and resulting international visibility reinforcethe confidence worldwide in SONANGOL's capabilities in oil fielddevelopment. It also brings Angola to the front, as a country where huge technologicalproject representing significant and risky financial investment can beactually, safely and promptly developed making the place appealing forinvestors. PAZFLOR is also a new benchmark in the maximization of using local industries, yards and talents, a priority for the country which intends to take advantageof its natural resources to favor the development of the economic andindustrial fabric. In this respect, as a consequence of the local content requirements imposed tothe Contractors, three yards (SONAMET, SONILS, PAENAL), one spool base (DANDE)and an umbilical factory in Lobito participated in the project and had theopportunity to extend their production capabilities, to procure employment to alarge number of workers and to improve their knowhow. For instance, Angoflexspool base in Dande was significantly up graded and FKIA stroke a new challengeby assembling PAZFLOR Xmas trees on SONILS' base. Also, the 4 million man-hours of Angolan content and the day to day operationof FPSO, obviously called for some highly qualified personnel.
- Africa > Angola (1.00)
- North America > United States > Texas > Harris County > Houston (0.16)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Africa Government > Angola Government (0.94)
Abstract The first deepwater geotechnical site investigations in Angola were conducted in 1998 on the Kuito and Girassol fields. Since that date, geotechnical data have been gathered in a large number of deepwater sites to support safe and economic design of many types of subsea infrastructures (anchors, sealines, subsea foundations …). The deepwater operators in Angola (BP Angola, CABGOC, Esso Exploration Angola, Total E&P Angola) set up an expert committee to agree on how to improve understanding of seabed soil conditions and their interaction with foundation structures for the deepwater Angola. The expert committee agreed on how the factual data collected would be combined in a single database and the task devoted to Angola Deepwater Consortium (ADC) to develop a Geographic Information System (GIS) containing information on geotechnical data against a background representing high resolution bathymetry and as-built facilities in the deepwater blocks. Fugro Geoconsulting Limited was chosen to construct the database and install it on the internationally well-known ArcGIS software which has been customized for this project. The Angolan GIS database represents an unprecedented gathering of factual data which can then be viewed, accessed and queried through a map-based user friendly interface. It helps experts for an improved region-wide understanding of soil conditions. In the early stage of future field developments, it helps making a preliminary assessment of soil data trends, seabed landscape and features and planning soil investigations. Currently, the database contains 40 site investigation projects and represents around 1000 information points (in-situ testing and borehole) and more than 70,000 individual measurements. It has been used to support a regional-wide geological desktop study and a preliminary analysis of soil conditions in deepwater Angola. The database is the result of exceptional cooperation between Angolan deepwater operators and a further objective is, for Sonangol, to operate and maintain this database in Angola which will provide a comprehensive, updatable and evolving repository of hard-won soils data relevant to future deepwater field developments offshore Angola. Introduction Background As part of a general effort to improve oil development in deepwater offshore Angola, Angola Deepwater Consortium (ADC) was formed in 2000 by Sonangol with industrial partners Doris Engineering and Pride Foramer. ADC has performed a number of studies under the guidance of a JIP Steering Committee composed of representatives and experts of BP, CABGOC, Esso Exploration Angola and Total E&P Angola (Da Costa & al., 2005).
- North America > United States > Texas (0.29)
- Africa > Angola > South Atlantic Ocean (0.24)
- Africa > Angola > South Atlantic Ocean > Lower Congo Basin > Block 17 > Girassol Field (0.94)
- Africa > Angola > South Atlantic Ocean > Lower Congo Basin > Block 14 > Kuito Field (0.94)
4D Seismic In Deep Water At the Dikanza Field, Offshore Angola, West Africa.
Mitchell, Paul (ExxonMobil Exploration Company) | Paez, Rachel (ExxonMobil Production Company) | Johnston, David (ExxonMobil Production Company) | Mohler, Gary (ExxonMobil Exploration Company) | Neto, Conceição da Cunha (Sonangol)
ABSTRACT The Dikanza field is located approximately 120 miles offshore West Africa in a water depth of 1100m. A 4D seismic program was acquired over the field with the objectives of monitoring water sweep, oil water contact (OWC) movement, gas exsolution, secondary gas cap formation and to identify infill well opportunities to optimize the field''s depletion plan and ultimate hydrocarbon recovery. The baseline seismic survey was acquired in 2002 as part of a larger high resolution exploration survey and the subsequent monitor survey was acquired in 2008, approximately two and a half years after the start of production in 2005. Excellent seismic repeatability was achieved with a normalized RMS (NRMS) value of around 0.1 in the shallow section above the reservoir after the fast-track processing and cross equalization. Dramatic production related 4D effects were observed in the data consisting of strong reflectivity changes and large time shifts associated with gas exsolution, water injection, water sweep and increases in pore pressure due to water injection. The observed 4D responses were validated by 4D forward seismic modeling and comparison to well production data and reservoir simulation results. The 4D data were then used to update and validate a new structural and stratigraphic interpretation of the field, to refine a new geologic model and to improve the accuracy of the corresponding reservoir simulation model. The 4D data generally confirmed the effectiveness of water sweep in the field and showed excellent agreement with the production data. It confirmed the presence of off-axis channel systems and indicated the presence of stratigraphic barriers to fluid flow. The 4D data also indicated that larger north-south trending faults were effective baffles to fluid flow whereas smaller east-west oriented faults were transmissible. Several new depletion well opportunities were identified including the relocation of a water injector away from a stratigraphie shale baffle and the addition of a new producer well to improve recovery from an un-swept area of the field.
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Geological Subdiscipline > Geomechanics (0.89)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.35)
- Geophysics > Time-Lapse Surveying > Time-Lapse Seismic Surveying (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
The Dalia Development Challenges and Achievements
Picard, D. (Total E&P Angola) | Thebault, J. (Total E&P Angola) | Goncalves, F.J. (Sonangol) | Costa, R. (Sonangol)
Abstract This paper sets the scene for a full suite of papers which will summarise the main challenges and achievements of the Dalia Development, which was managed by an integrated project team. An overview of the development will be presented in this paper, which will be complemented by a further six papers providing details covering:Subsurface, Drilling and Well Completions System Design and Flow Assurance Subsea Production System Flowlines, Risers and Umbilicals FPSO Oil Offloading Export System Spanning from pre-award to first oil, this paper will highlight some of the many challenges faced, describe the major technological innovations adopted (including some "world firsts". It will also comment on how lessons learned from Girassol development were incorporated, and comment on HSE management, the development schedule and contracting strategy. Finally the integration of the project into Angola including the new industrial bases, training and environmental commitment will be described. Introduction Setting the Scene Building on the success of Girassol, Total have continued, together with the Concessionaire and Partners, to push the boundaries of deep water technology in the Dalia development, by using innovative technology to execute this multi-well heavy oil development. The development has been performed in accordance with the Company HSE and Quality Charters. The field is located 210 km north west of Luanda, about 140 km from shore (Figure 1). It was the second major discovery out of 15 made in the prolific Block 17 (Figure 2). Figure 1 - Block 17 Geographical Location and Reservoirs(available in full paper) The project chronology has been marked by some significant dates:1997: Field discovery 1999: Declaration of commercial discovery 2003: Project launch 2005: Commencement of drilling campaign 2006: Offshore installation 13th December 2006: First Oil Dalia is a large and complex field by many measures:Dalia is estimated to contain close to 1 billion barrels of recoverable oil in a reservoir extending some 230 km only 800 metres below sea bed in water depths of between 1,200 to 1,400 metres Heavy oil at 21° API compared to 32° API on Girassol The development scheme is based on 71 subsea completed wells: 37 producers, 31 water injectors and 3 gas injectors.The production wells are set in clusters around nine manifolds on four pipe in pipe production flow loops. Each manifold is capable of connecting up to six wells The water injection wells connect to four water injection lines via inline tees The gas injection wells connect to two gas injection lines via inline tees The subsea network links to the FPSO via flexible risers The FPSO is a large new build vessel with an oil processing capacity of an average 240,000 barrels per day, water injection of 405,000 barrels per day and gas compression capacity of 8 million standard cubic metres per day. The FPSO oil storage capacity is two million barrels Oil export is performed via an offloading buoy Integrated Teams In order to bring such a large field on stream in deep waters, it has been necessary to develop and qualify new technologies, new equipment and address a number of key issues such as reservoir uncertainties and flow assurance.
- North America > United States > Texas (0.28)
- Africa > Angola > Luanda Province (0.25)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Management > Strategic Planning and Management > Project management (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Risers (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Floating production systems (1.00)
Abstract: A lithoseismic characterization allowed us to map sandstone distribution preditected through seismic facies analysis and to characterize the porosity. Well data alone cannot accurately recover the requested property variations, because of their sparse lateral distribution and their large spacing, compared to the size of the lateral heterogeneities to be modeled. On the opposite and despite its poor vertical resolution, seismic data provide valuable information to overcome such a limitation as it benefits from the highest lateral density of information. Accurate descriptions of the lateral variation of reservoir heterogeneities is a critical issue when generating reservoir models dedicated to history matching and subsequent production forecasts. This poster describes one of the workflow that has been successfully applied on a turbidite in Angola, which allows (1) extracting reliable constraints from post-stack seismic amplitudes and (2) incorporating them into high-resolution geological models for quantitative lithoseismic reservoir characterization. Relevant constraints are generated using lithoseismic reservoir characterization techniques, based on seismic inversion followed by seismic facies analysis, generation of net-to-maps and porosity models. Then, for reservoir geological modeling, we selected a pluri-gaussian modeling approach, which provides the requested level of flexibility for mixing the obtained map with well data and thus solving the downscaling issues. Case study The example used for illustrating the modeling workflow described in this poster is a turbidite field, Deep water Offshore Angola. The data set used is the following:–3D post-stack seismic volume; –8 wells with a full set of logs, including sonic, density, gamma ray, resistivity and neutron porosity; –The reservoir top and bottom in both time and depth. Extracting the relevant seismic constraints The quantitative lithoseismic characterization work starts with a two approaches:Qualitative constraints, when inversion is followed by seismic facies analysis. Interpreted seismic facies maps are used to define the geological zonation of the reservoir. Quantitative constraints consist of facies/geological rock type proportion maps, generated from geological calibration of post-stack seismic attributes at wells and statistical regression of geostatistical modelling techniques. In the example used for to illustrate this poster, both kinds of constraints have been used simultaneously. No reliable quantitative relationship can be built between seismic attributes and reservoir properties at wells, because the heterogeneity of the reservoir under study. Consequently, a seismic facies analysis is performed to obtain a reservoir zonation map. This map is then converted into sand proportion map by calibrating the seismic facies against well data. The technique we used is a non-supervised statistical pattern recognition approach, based on the analysis of the multivariate probability density function of the seismic attributes. This analysis allows identify the number of natural clusters in the data, each mode corresponding to a specific shape of the traces. The most typical traces of each mode are extracted and then used in discriminante analysis. At this step two maps were generated: a facies map and a probability map that gives information on the confidence in the classification.
- Africa > Angola (0.97)
- North America > Canada > Alberta > Woodlands County (0.25)
- Geophysics > Seismic Surveying > Seismic Processing > Seismic Migration (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation (1.00)
Abstract: A significant part of any field development planning exercise resides in adequately quantifying reservoir uncertainty, particularly when information availability is limited. For marginal fields, accurate appraisal of the downside of a project becomes even more crucial, as different development options carry a significant probability of negative net-present-value and project economic viability relies on reservoir risk minimization. It is then imperative to undertake a complete and detailed risk analysis, in order to identify key contributors to reservoir uncertainty, their combined effect and their impact on the final economic outcome. A thorough understanding of the risk setting can lead to resources being better focused, data acquired and creative solutions found, thereby mitigating the uncertainty and shifting the Gaussian distribution of recovery and net-present-value to the right. The evaluation and quantification of the impact of key uncertainty factors is exacerbated by the multiplicity of combinations in development options and can only be represented by a very high number of simulations. It is only with today's computing power and recent software developments, in stochastic data analysis and statistical optimization, that it is possible to quickly and exhaustively encompass all relevant uncertainty parameters. The following case of a marginal offshore field in Angola illustrates the successful application of a stochastic planning approach in defining the optimum field development strategy. A novel workflow in stochastic analysis was applied allowing proper identification and mitigation of all relevant risk factors. This resulted in the determination of optimum surface facilities dimensions, well locations, drilling plans, wellhead structure locations, coring programs and logging suites. This methodology was key in establishing an economically viable option in this high cost, high-risk area. INTRODUCTION The Morsa-West field was discovered in the early 80's, offshore Angola, and delineated four separate hydrocarbon-bearing accumulations with a total of eight exploratory and appraisal wells. The formation types vary from sand (S) to sandy dolomite (SD) to predominantly dolomite (D) with productivities ranging from fair to good depending on the different geological environment and the presence of tectonically created fractures. The original operator attempted to put forward a viable development plan but had to relinquish operatorship as no economic solution was reached. Sonangol P&P, the operating arm of Sonangol, took it upon itself to investigate the development of this potential and completed a subsurface evaluation of the area. This evaluation concluded that five of the eight wells drilled encountered oil and the four confirmed accumulations could potentially be developed economically. Simultaneously, oil-bearing exploratory prospects were identified in the area providing further need for project implementation. Following this work, Sonangol P&P approached the Concessionaire and was granted the right to review the information and propose a field development plan for the Morsa-West area. The following work is a culmination of the efforts, put forward by the Sonangol sub-surface Team, to develop what was previously labelled as a marginally economic field into a profitable venture for Sonangol P&P. Definition of Risk Two types of risk exist at the Field Development level, Market Risk and Project Risk.