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Abstract This research proposed an alternative method for determining the saturation exponent (n) by finding the best correlations for the heterogeneity index using available core data and considering wettability changes. The log curves of the variable n were estimated, and the effect on the water saturation (Sw) calculations and the Stock Tank Oil Initially In Place (STOIIP) in the Tambaredjo (TAM) oil field was analyzed. Core data were employed to obtain the relationship between n and heterogeneity using cross-plots against several heterogeneity indices, reservoir properties, and pore throat size. After filtering the data, the clay volume (Vcl), shale volume, silt volume, basic petrophysical property index (BPPI), net reservoir index, pore grain volume ratio, and rock texture were defined as the best matches. Their modified/improved equations were applied to the log data and evaluated. The n related to Vcl was the best selection based on the criteria of depth variations and logical responses to the lithology. The Sw model in this field showed certain log readings (high resistivity [Rt] reading ≥ 500 ohm.m) that infer these intervals to be probable inverse-wet (oil-wet). The cross-plots (Rt vs. Vcl; Rt vs. density [RHOB]; Rt vs. total porosity [PHIT]) were used to discard the lithologies related to a high Rt (e.g., lignites and calcareous rocks) and to correct Sw when these resulted in values below the estimated irreducible water saturation (Swir). The Sw calculations using the Indonesian equation were updated to incorporate n as a variable (log curves), comparing it with Sw from the core data and previous calculations using a fixed average value (n = 1.82) from the core data. An integrated approach was used to determine n, which is related to the reservoir’s heterogeneity and wettability changes. The values of n for high Rt (n > 2) intervals ranged from 2.3 to 8.5, which is not close to the field average n value (1.82). Specific correlations were found by discriminating Swir (Swir < 15%), (Swir 15%–19%), and Swir (> 19%). The results showed that using n as a variable parameter improved Sw from 39.5% to 36.5% average in the T1 and T2 sands, showing a better fit than the core data average and increasing the STOIIP estimations by 6.81%. This represents now a primary oil recovery of 12.1%, closer to the expected value for these reservoirs. Although many studies have been done on n determination and its effect on Sw calculations, using average values over a whole field is still a common practice regardless of heterogeneity and wettability considerations. This study proposed a method to include the formation of heterogeneity and wettability changes in n determination, allowing a more reliable Sw determination as demonstrated in the TAM oil field in Suriname.
Guyana's President Irfaan Ali announced that the first phase of the Liza offshore crude project had achieved its intended full-production capacity of around 130,000 B/D. Ali told virtual attendees at the Guyana Basin Summit that he expected an additional 10 exploration and appraisal wells to be drilled off Guyana this year. He said the second phase of the Liza project, operated by ExxonMobil, would begin in 2022. The consortium led by Exxon, which includes partners Hess and CNOOC Ltd., has made 18 discoveries containing more than 8 billion bbl of recoverable oil and gas in Guyana's Stabroek block.
Exxon encountered noncommercial hydrocarbons with a test of its Bulletwood prospect in the Canje Block in the Guyana-Suriname basin. The well, located in 2846 m of water, was drilled to its planned target depth of 6690 m using drillship Stena Carron. Data collection from the Bulletwood-1 well confirms the presence of the Guyana-Suriname petroleum system and the potential prospectivity of the Canje Block, said partner Westmount Energy. Bulletwood-1 was the first of three scheduled wells to be drilled on the block in 2021. Wells Jabillo-1 and Sapote-1 are expected to spud over the coming months.
Geoscientist Kerry Moreland was ExxonMobil's exploration manager for the Guyana/Suriname Basin from 2014 to 2018, when the energy giant confirmed multiple discoveries, including the world-class Liza-1 find, where for decades drillers hit mostly dry holes. After a stint as West Africa exploration manager and Africa geoscience manager for development and production, Moreland was promoted to her current position: vice president, Sub-Sahara Africa and Asia Pacific, exploration and new ventures, ExxonMobil Upstream Business Development Co. Today, Moreland manages ExxonMobil's oil and gas exploration acreage and evaluates new opportunities across the industry's two most important frontier energy landscapes--Asia Pacific and Africa, which are destined to see the highest growth in energy demand by 2050 as well as present the greatest challenges for managing energy supply in a dual energy environment. This week, Moreland discussed her company's current successes and future vision in one of a series of IPTC Insights interviews conducted by a moderator with thought leaders at the International Petroleum Technology Conference (IPTC) in Kuala Lumpur. Here, JPT reports the highlights of Moreland's interview. IPTC: In January 2020, ExxonMobil increased its estimated recoverable resource base in Guyana to more than 8 billion oil equivalent barrels and announced its 18th discovery in September 2020 at the Redtail-1 well on the Stabroek Block.
ExxonMobil made its ninth discovery offshore Guyana, possibly creating the greatest value of any offshore basin in the Americas. This is the company's fifth discovery on the Stabroek Block in the past year and proves a new play concept for potential development. The Hammerhead-1 discovery encountered approximately 197 ft (60m) of high-quality, oil-bearing sandstone reservoir. The well was safely drilled to 13,862 ft (4,225m) depth in 3,373 ft (1150m) of water. "The Hammerhead-1 discovery reinforces the potential of the Guyana basin, where ExxonMobil is already maximizing value for all stakeholders through rapid phased developments and accelerated exploration plans," said Steve Greenlee, president of ExxonMobil Exploration Company.
Malaysian oil company Petronas has hired Maersk Drilling's rig Maersk Developer for a one-well exploration campaign off the coast of Suriname. The campaign will take place in Block 52 which covers an area of 1,834 sq mi in the Suriname-Guyana basin. Maersk Drilling said the contract is expected to start in Q3 or Q4 2020, with an estimated duration of 75 days. The value of the contract is approximately $20.4 million, including integrated drilling services, mobilization, and demobilization fees. The contract includes an additional one-well option.
Could 2019 be a bumper year for offshore energy development? In just the first few weeks of this year, four discoveries in the UK North Sea and offshore Guyana and South Africa found 1.3 billion BOE--25% of the approximately 5.3 billion BOE high-impact volume discovered globally in the whole of 2018--according to Westwood Global Energy Group. Westwood has identified another 78 high-impact exploration wells either currently being drilled or planned for the remainder of 2019. The expected gross unrisked volume of oil and gas from the 78 wells is 23 billion BOE. More than half the wells are in deep water (Figure 1).
Interbedded formations are challenging to drill due to its potential to trigger torsional instability issues while drilling at low depth-of-cut (DOC), which could damage the bit due to impact and result in low penetration rate or an undesired trip. Wells drilled in the Guyana-Suriname Basin face a similar challenge as the wells penetrate interbedded shale and carbonates, causing conventional polycrystalline diamond compact (PDC) bits to lose their cutting efficiency due to impact damage while drilling the hard, interbedded formation.
Using a detailed bench-marking methodology, offset drilling data was analyzed and the results were utilized to optimize bit design to meet these challenges. Mechanical specific energy (MSE), which quantifies drilling efficiency, indicates formation changes and signals the advanced dull condition or damage. When coupled with dull bit forensics, MSE provides insight for iterative bit design optimization to mitigate drilling challenges.
The outcome of a detailed benchmarking process led to the selection and deployment of a 12¼-in. hybrid bit to drill directionally through interbedded formation, which significantly improved drilling performance and bit durability. The hybrid bit combined PDC and tungsten carbide insert (TCI) rolling cutting elements and delivered balanced aggressiveness to improve torisonal stability. Post-well analysis showed rolling DOC control offered by the hybrid bit delivered higher penetration rate. The comparison of the drilling mechanics of the hybrid versus PDC highlighted limited drilling efficiency of PDC bits in interbedded formation. The hybrid bit drilled 54% more carbonates than the best PDC offset run. Drilling dynamics data also highlighted lower levels of vibrations with the hybrid bit. In addition, the hybrid dull condition was better than the PDC bits, suggesting improved durability compared to the previously-used PDC bits.
This paper demonstrates time and depth based surface and downhole drilling data, when supplemented with rock strength analysis using a suitable benchmarking process, can provide insight about drilling mechanics. When matched with an application specific bit, it leads to sustained drilling performance improvement.
The objective of this study was to characterize formation water resistivity (
A database with analyzed water sample and log-derived (Dielectric and Conventional logs)
Creating the WSA tool was very important to determine which samples were ionic balanced and were useful for further steps. These samples delivered different salinities which could clarify the water sources for the produced sand intervals. Three main groups of water sources were established based on the salinity; S-sands, T-sands and Cretaceous. Based on this classification, the log derived
Regarding stock tank oil initially in place (STOIIP) in TCA, with the variable
Formation water salinity is a very important input in