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Wandoo B is a concrete gravity-based structure (GBS) and is the main production facility for the Wandoo field offshore northwest Australia. It was installed in 1997 with a design life of 20 years. The structural assessments discussed in this paper are part of a comprehensive life-extension project encompassing wells, subsea systems, marine and safety systems, and topsides facilities and structures to demonstrate fitness for service through the end of field life. The GBS serves as the support structure for the Wandoo B facility and provides oil storage for the Wandoo field. The structure has four shafts approximately 11 m in diameter that support the topsides facilities and a base structure with permanent ballast and oil storage cells (Fig.
Wheatstone and Iago gas fields, part of the larger Wheatstone project, commenced production in June 2017. The foundation subsea system includes nine Wheatstone and Iago development wells tied back to a central Wheatstone platform (WP) for processing. Hydrocarbons then flow through an export pipeline to an onshore processing facility that includes two liquefied-natural-gas (LNG) trains and a domestic gas facility. The complete paper highlights some of the key learnings in well and reservoir surveillance analysis and optimization (SA&O) developed using data from early production. Chevron Australia's Wheatstone project is in the North West Shelf region offshore Australia (Figure 1).
Abstract Faulting is one type of structural trap for hydrocarbon reservoirs. With more and more fields moving toward the brownfield or mature operations stage of life, the opportunity to target bypassed or attic oil in the vicinity of bounding fault(s) is becoming more and more attractive to operators. However, without an effective logging-while-drilling (LWD) tool to locate and map a fault parallel to the well trajectory, it has been challenging and potentially high risk to optimally place a well to drain oil reserves near the fault. Operators often plan these horizontal wells at a significant distance away from the mapped fault position to avoid impacts to the well construction and production of the well. Often, the interpreted fault position, based on seismic data, can have significant lateral uncertainty, and uncertainties attached to standard well survey measurements make it challenging to place the well near the fault. This often results in the wells being placed much farther from the fault than expected, which is not optimal for maximizing recovery. In other cases, due to uncertainty in the location of the fault, the wells would accidentally penetrate the side faults and cause drilling and other issues. Conventional remote boundary detection LWD tools do not assist with locating the fault position, as they only detect formation boundaries above or below the trajectory and not to the side. In this paper, the authors propose a novel approach for mapping features like a fault parallel to the well trajectory, which was previously impossible to map accurately. This new approach utilizes a new class of deep directional resistivity measurements acquired by a reservoir mapping-while-drilling tool. The deep directional resistivity measurements are input to a newly devised inversion algorithm, resulting in high-resolution reservoir mapping on the transverse plane, which is perpendicular to the well path. These new measurements have a strong sensitivity to resistivity in contrast to the sides of the wellbore, making them suitable for side fault detection. The new inversion in the transverse plane is not limited to detecting a side fault; it can also map any feature on the transverse plane to the well path, which further broadens the application of this technology. Using the deep directional resistivity data acquired from a horizontal ultra-ERD well recently drilled in the Wandoo Field offshore Western Australia, the authors tested this approach against the well results and existing control wells. Excellent mapping of the main side fault up to 30 m to the side of the well was achieved with the new approach. Furthermore, the inversion reveals other interesting features like lateral formation thickness variations and the casing of a nearby well. In addition, the methodology of utilizing this new approach for guiding geosteering parallel to side fault in real time is elaborated, and the future applications are discussed.
Abstract Fracture treatments and stage designs for new wells have evolved considerably over the past decade contributingto significant production growth. For example, in the acreage discussed hererecently used higher intensity fracturing methods provided an ~80% increase in recovery rates compared with legacy wells. Older wells completed originally with less efficient techniques can also benefit from these more up-to-date designs and treatments using re-fracturing methods. These offer the prospect of economically boosting production in appropriately selected wells. While adding in-fill wells has often been favored by Operators as a lowerrisk option the number of wells being re-fractured has grown every year for the last decade. In this case study two adjacent Eagle Ford wells, comprising a newly completed and a re-fractured well, allow both methods to be considered and compared. Completion design and fracture treatment effectiveness are evaluated using the uniformity of proppant distribution at cluster and stage level as the primary measure. Perforation erosion measurements from downhole video footage is used as the main diagnostic. Novel data acquisition methods combined with successful well preparation provided comprehensive and high-quality datasets. The subsequent proppant distribution analysis for the two wells provides the highest confidence results presented to date. Clear, repeatable trends in distribution are observed and these are compared across multiple stage designs for both the newly completed and re-fractured well. Variations in design parameters and how these effects distribution and ultimately recovery are discussed. These include changes to perforation count per cluster, cluster spacing, cluster count per stage, stage length, perforation charge size and treatment rates and volumes. As a final consideration production records for the evaluated wells are also discussed. Historical industry data shows that the number of wells being re-fractured increases relative to the number of newly drilled wells being completed during periods of low oil and gas prices. With the industry again facing harsh economic realities an increasing number of decisions will be made on whether new or refractured wells, or a combination of both, provide the best solution to replace otherwise inevitable production decline. This paper attempts to provide a detailed understanding of how proppant distribution, as a significant factor in production for hydraulically fractured wells, can be evaluated and considered in these decisions.
Abstract This paper investigates the technology and business benefits of a web-based model scheduling application, which integrates a transient model to other business applications that provide injection and demand schedules. The application provides a simple method to input complex scenarios, including compressor, regulator, and routing operations. The paper shows how the system allows non-modellers to use a complex transient model, reducing non-optimal operational decisions which could impact the wholesale natural gas price or supply to end user customers such as households or businesses. Other operational metrics are discussed. Introduction and Background Independent System Operators’ (ISOs) and Transmission System Operators’ (TSOs) use of transient pipeline models to manage nominations and allocations is seemingly an easy operational premise. The Australian Energy Market Operator (AEMO) operates the gas Declared Transmission System (DTS) which serves Victoria, a state in Australia. The DTS network consists of approximately 2,200 km of transmission pipelines with various lengths and diameters, and transports gas to a network from up to 10 different suppliers. The high pressure meshed transmission network supplies gas to 148 custody transfer points which spans the geographical extremities of the state. The DTS is becoming increasingly more complex, with changes to flow paths and dynamic demand regimes. AEMO, like other TSOs and ISOs, is utilising transient pipeline models to inform operational strategies. This paper explores the challenges facing ISOs and TSOs in the United Kingdom, The United States, and Victoria Australia. Specific reference is made to AEMO’s gas transmission network. The issues explored cover a range of subjects including financial and macro policy but all lead to the impact on a transmission network. The paper does not attempt to solve each transmission operator’s challenges in detail. However, within the context of AEMO’s operations, it attempts to identify the similarities with other TSOs and highlight how AEMO’s transient hydraulic model helps it deal with its challenges.
The complete paper describes the extensive integrated engineering collaboration and optimization process that allowed an operator to push the drilling and completion envelope to drill a pair of complex, ultra-extended-reach-drilling (ERD) wells in the mature Wandoo field in the Carnarvon Basin offshore Western Australia. The shallow reservoir depth, extreme ERD profile, and high tortuosity requirement for the wells posed significant challenges. These were overcome with extensive planning; integrated engineering designs; application of new technology; good-quality, real-time data interpretation; and strong execution support from both rig site and town. The Wandoo field, in 56 m of water offshore Western Australia, was discovered in 1991 and subsequently developed and placed on production in 1993. The shallow unconsolidated sandstone reservoir consists of a heavily biodegraded oil column overlain by a gas cap and supported by a strong aquifer drive.
Abstract Northern Carnarvon Basin is located in North West Shelf of Western Australia. The basin has over 10km sediments and owns both oil-prone and gas-prone sediments and is the current largest oil and gas producing basin in Australia. A geological section through this basin is shown in Figure 1, the complex geological settings from shallow to deep leads to significant processing challenges. In the vintage processing, the seismic image at reservoir level is deteriorated due to the presence of following geological complexities: 1) rugose water bottom, 2) shallow frequent canyons or channel systems, 3) shallow spatial-variant Tertiary carbonates, and 4) shallow gas chimneys and other geo-bodies. These complex overburdens plus limited small-angle coverage of primary reflections from narrow azimuth (NAZ) streamer surveys make it very difficult for ray-based reflection tomography to resolve the shallow velocity. As a result, the target image suffers from large well mis-ties, low signal-to-noise ratio (S/N) and severe event undulations. In addition, shallow fast-velocity layers cause severe illumination issues for deep targets which are compounded by limited offsets of NAZ surveys. Furthermore, localised absorption effects from gas pockets lead to dimming amplitudes for events beneath them. To deal with these issues, we propose to use time-lag full wave-form inversion (TLFWI) to resolve the velocity of complex overburdens and least-squares Q prestack depth migration (LS Q-PSDM) to compensate for illumination issues and absorption effects for the latest reprocessing. In the following sections, application procedure and results of these two technologies will be discussed. Seismic inversion was also conducted to assist the processing and analysis of the final result.
Abstract The North West Shelf of Australia contains a late Paleozoic to Cenozoic sedimentary succession, which attains a thickness of over 10 km and is dominated by Triassic to Lower Cretaceous sediments. The deeper plays exist at multiple stratigraphic levels including oil-prone Jurassic sediments and faulted gas-prone Triassic sediments. The area has been proven difficult as far as seismic imaging is concerned, particularly over the Madeline trend. The presence of a hard, rugose water bottom, strong reflectors beneath the water bottom, and shallow Tertiary carbonates make the Dampier Sub-basin vulnerable to multiple contamination, amplitude distortion, lower signal-to-noise ratio (S/N) and unreliable AVO response. Poor seismic quality in the data has been a significant barrier to reducing exploration risk. In the 1990s, East Dampier (1992, blue polygon in Figure 1) and Keast (1997, yellow polygon in Figure 1) seismic data were acquired in East-West and North-South directions respectively, in an effort to better understand the impact from the shallow complex overburden. To address these challenges, the Demeter survey was acquired in 2003 (black polygon in Figure 1) with a denser acquisition grid. The overall seismic quality was improved, but the results still contained a significant level of residual multiples. Later, the Fortuna survey, the most comprehensive multi-sensor seismic survey on the North West Shelf of Australia to date, was acquired in 2014 with the aim to provide better subsurface imaging (pink polygon in Figure 1) from different acquisition perspectives. The data was processed with advanced processing technology, including shallow water demultiple, deghosting and high definition tilted orthorhombic velocity model building (Birdus et al., 2017). However, the final results were still suffering from a number of challenges, specifically: 1) strong residual multiple in near offsets, 2) low S/N ratio, particularly at reservoir level, and 3) inconsistency from near to far stack resulting in unreliable AVO. In this paper, the Dixon area (green polygon), considered as the most challenging area in the Dampier Sub-basin, was chosen as the testing area for our work. By integrating high-end imaging technology, for example dual-sensor deghosting, multi-survey surface related multiple elimination (MAZ-SRME), and multi-azimuth processing (MAZ stack), we will illustrate how we have overcome many of these imaging challenges.
KrisEnergy Pumps Cambodia’s First Crude in 17 Years A Cambodian concession has commenced production after years of delays in a venture between Singapore’s KrisEnergy and the government. The crude comes from oil fields in Block A, comprising 3083 km of the Khmer basin in the oil-rich Gulf of Thailand, off the southwestern coast of Sihanoukville. The concession will progress in phases once new wells are commissioned and completed. Kelvin Tang, chief executive of KrisEnergy’s Cambodian operations, called the 29 December event “an important strategic milestone” for the company, while Prime Minister Hun Sen hailed the first extraction as “a new achievement for Cambodia’s economy” and “a huge gift for our nation.” Ironbark Australian Exploration Well Declared Dry; Co-Owner Stocks Plummet BP has come up dry at its Ironbark-1 exploration well, the anticipated multi-trillion-scf prospect off the west Australian Pilbara coast. The disappointing prospect was once seen as a potential gas supplier to the emptying North West Shelf (NWS) LNG plant, where BP is a co-owner, within 5 to 10 years. After 2 months of drilling to a total depth of 5618 m, “no significant hydrocarbon shows were encountered in any of the target sands,” according to co-owner New Zealand Oil and Gas (NZOG). Petrorecôncavo Buys Petrobras’ Onshore Bahian Stake for $30 Million Brazilian operator Petrobras on 23 December signed a contract with independent producer Petrorecôncavo to sell its entire stake in 12 onshore E&P fields, the Remanso Cluster, in the state of Bahia. The sale value for the fields was $30 million; $4 million was paid on signing, $21 million at the closing of the transaction, and $5 million will be paid 1 year after that. The Remanso Cluster comprises the onshore fields of Brejinho, Canabrava, Cassarongongo, Fazenda Belém, Gomo, Mata de São João, Norte Fazenda Caruaçu, Remanso, Rio dos Ovos, Rio Subaúma, São Pedro, and Sesmaria. Zion Spuds the Israeli Megiddo-Jezreel #2 Well On 6 January, Zion Oil and Gas officially spudded the MegiddoJezreel #2 on its 99,000acre MegiddoJezreel license area in Israel. “With unique operating conditions in the COVID19 environment, our crews have performed an amazing task,” Zion CEO Robert Dunn said. “Mobilizing a rig into a new country during a pandemic and rigging up is the most challenging part of the drilling operation,” Zion’s vice president of operations, Monty Kness, added. Exxon Declares a Dud at Second Guyana Well Exxon Mobil said on 15 January that its exploration well in the prolific Stabroek Block off Guyana’s coast did not find oil in its target area. Exxon, which operates the Stabroek Block in a consortium with Hess and China’s CNOOC, has made 18 discoveries in the area in 5 years, totaling more than 8 billion BOE, for a combined potential for producing up to 750,000 B/D of crude. The Hassa1 exploration well was the giant’s second setback to its drilling campaign in recent months. Heirs Holdings Buys 45% of Shell Nigeria’s OML 17 Field Shell Nigeria announced on 15 January it had completed a $533 million sale of its stakes in an onshore OML 17 oil field in Nigeria to African strategic investor Heirs Holdings, Nigeria’s largest publicly listed conglomerate. The deal is one of the largest oil and gas financings in Africa in more than a decade, with a financing component of $1.1 billion provided by a consortium of global and regional banks and investors. Heirs Holdings, in partnership with Transcorp, one of the largest power producers in Nigeria with 2000 MW of installed capacity, purchased 45% stake in the field. It acquired the stakes of Shell, Total, and Eni to further its expansion into the oil and gas industry. Apex Discovers Oil in Egypt’s Western Desert Privately held independent E&P firm Apex International Energy, backed in part by UK energy investment firm Blue Water Energy, on 18 January announced a discovery in the Southeast Meleiha Concession (SEM) in the western desert of Egypt. The discovery was made at the SEMZ-11X well located 10 km west of Zarif field, the nearest producing field. The well was drilled to a total depth of 5,700 ft and encountered 65 ft of oil pay in the Cretaceous sandstones of the Bahariya and Abu Roash G formations. Testing of the Bahariya resulted in a peak rate of 2,100 B/D with no water. Additional uphole pay exists in the Bahariya and Abu Roash G formations that can be added to the production stream in the future. Kosmos Announces Oil at Winterfell Well Dallas-based E&P independent Kosmos Energy announced on 19 January an oil discovery in deepwater US Gulf of Mexico. The Winterfell discovery well, the product of infrastructure-led exploration (ILX), was drilled to a total depth of approximately 23,000 ft and is located in approximately 5,300 ft of water. This subsalt Upper Miocene prospect in off-shore Louisiana encountered approximately 85 ft of net oil pay in two intervals. ILX exploration, which has featured prominently in upstream operators’ portfolios in recent years of relatively low oil prices, is exploration around producing hubs that can be hooked up to those facilities easily and cheaply. The development sidesteps the need for costly and time-consuming individual hub construction. Equinor Gets Permit To Drill North Sea Wildcat Well The Norwegian Petroleum Directorate has granted Equinor a drilling permit for wildcat well 31/11-1 S in the North Sea offshore Norway, 62 km south of the Troll field. The drilling program is the first exploration well to be drilled in production license 785 S, awarded on 6 February 2015 (APA 2014). Operator Equinor and Total E&P Norge are 50/50 partners in the license, which consists of parts of Blocks 26/2 and 31/11. Petrobras, ExxonMobil Hit Hydrocarbons at Urissanê Well, Offshore Brazil Brazilian state-owned Petrobras announced on 29 January it had discovered hydrocarbons in a well located in the Campos Basin presalt off Brazil’s coast of Campos dos Gotyacaze in the State of Rio de Janeiro. Well 1-BRSA-1377-RJS (informally called Urissanê) is located in Block C-M-411, at a depth of 2950 m approximately 200 km offshore. Petrobras, which operates the block in a 50/50 partnership with Exxon Mobil, said it would analyze the well data to better target exploratory activities and assess the potential of the discovery. BP Offloads 20% Share of Oman’s Block 61 To PTTEP Marking another significant step in its divestment program, BP will sell a 20% participating interest in Oman’s 3950 km Block 61 in central Oman to Thailand’s national PTT Exploration and Production (PTTEP) for $2.59 billion. BP will remain operator of the block, holding a 40% interest. The sale comprises $2.45 billion payable on completion and $140 million payable contingent on preagreed conditions. After the sale, BP will hold 40% interest in Block 61, while OQ holds 30%, PTTEP 20%, and Petronas 10%. Block 61 contains the largest tight gas development in the Middle East.
Summary Identification of vuggy intervals and understanding their connectivity are critical for predicting carbonate reservoir performance. Although core samples and conventional well logs have been traditionally used to classify vuggy facies, this process is labor intensive and often suffers from data inadequacies. Recently, convolutional neural network (CNN) algorithms have approached human-level performance at multiimage classification and identification tasks. In this study, CNNs were trained to identify vuggy facies from a well in the Arbuckle Group in Kansas, USA. Borehole-resistivity images were preprocessed into half-foot intervals; this complete data set was culled by removing poor-quality images to generate a cleaned data set for comparison. Core descriptions along with conventional gamma ray, neutron/density porosity, photoelectric factor (PEF), and nuclear magnetic resonance (NMR) T2 data were used to label these data sets for supervised learning. Hyperparameters defining the CNN network size (numbers of convolutional layers/filters and the numbers of fully connected layers/neurons) and minimize overfitting (dropout rates, patience, and minimum delta) were optimized. The median losses and accuracies from five Monte Carlo realizations of each hyperparameter combination were the metrics defining CNN performance. After hyperparameter optimization, median accuracy for vuggy/nonvuggy facies classification was 0.847 for the cleaned data set (0.813 for the complete data set). This study demonstrated the effectiveness of using microresistivity image logs in a CNN to classify facies as either vuggy or nonvuggy, while highlighting the importance of data quality control. This effort lays the foundation for developing CNNs to segment images to estimate vuggy porosity.