The Development of a Novel Log Based Permeability Transform for a Mature Carbonate Reservoir and its Significance in Explaining the Water Flood EOR Response

Michael, Dowen; AlAli, Abdulkarim; Nemmawi, Nadia

doi:10.2118/194875-ms

Cited by 3 publications

(2 citation statements)

References 3 publications

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“…The fluid dynamics in these reservoirs are complex. For instance, in the mature Mauddud reservoir, vertical and horizontal oil migrations, and aquifer influx on the reservoir's edge, follow the gas injection [53].…”

Section: A Geology and Oil Productionmentioning

confidence: 99%

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Nationwide Subsidence in Bahrain Island: Drivers and Implications for Relative Sea-Level Rise

Normand

Heggy

Castellazzi

2023

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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The IPCC-AR6 report suggests that the sea-level in the Persian Gulf is expected to rise by 2.1-4.9mm/year by 2100, which is lower than the global projections of 4-14mm/year. However, a central nationwide ground subsidence in Bahrain's low-lying island can aggravate these figures. The island is only 14-kilometers-wide, yet we observe a 7×12-kilometer ground subsidence with vertical rates up to 20mm/year for 2016-2021. To characterize the subsidence, we use the following methods: (i) SBAS-InSAR with 94 and 131 C-band Sentinel-1A orbital radar acquisitions in ascending and descending directions for 2016-2021, respectively, and (ii) Stacking-InSAR with eight L-band ALOS-1-PALSAR acquisitions for 2007-2010 and six ALOS-2-PALSAR-ScanSAR acquisitions for 2016-2021. Although the observed subsidence velocities are non-linear, we estimate a subsidence of up to 1.5-meters by 2100 by extrapolating the average rates. We suggest three causes associated with this subsidence: (i) Exploitation of the Awali oil field, (ii) Local aquifer depletion, and (iii) Subsurface dissolution of anhydrites and chalky-limestones. To assess the potential impact of subsidence on the shoreline, we measure the coastline evolution at three undisturbed beaches on the West-coast from 1985-to-2021, excluding areas that underwent land-reclamation. Using sub-pixel shoreline detection analysis from 308 Sentinel-2 and Landsat (L5, L7, and L8) acquisitions, we observe that the selected shores remain stable. However, observations reveal a shoreline retreat of up to 5m/year on the southwestern coast for 2003-2014. This rate exceeds the modeled rate of 0.85m/year derived solely from local tide gauge sea-level measure. This nationwide subsidence should be considered when forecasting coastal infrastructure-planning in Bahrain. We recommend performing a similar analysis in other lowlying Gulf islands where oil exploitation occurs.

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Section: A Geology and Oil Productionmentioning

confidence: 99%

“…2. On Oil production Faults, fractures, anticline structure, and permeable layers heterogeneity control the gas cap distribution and water ingress in reservoirs [53]. These fractures can develop, and new ones can appear when ground subsidence occurs over oil fields [3].…”

Section: On Coastal Floodingmentioning

confidence: 99%

Nationwide Subsidence in Bahrain Island: Drivers and Implications for Relative Sea-Level Rise

Normand

Heggy

Castellazzi

2023

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Understanding Mauddud Waterflood Performance in a Heterogeneous Carbonate Reservoir with Surveillance Data and Ensemble of Analytical Tools

Konwar

AlOwainati

Nemmawi

et al. 2020

Day 1 Mon, November 09, 2020

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Bahrain oil Field being the first oil discovery in the gulf region in 1932 is now in a mature stage of development. Crestal gas injection in the oil bearing, under saturated, layered and heavily faulted carbonate Mauddud reservoir has continued to be the dominant drive mechanism since 1938. Thirty-eight 40-acre 5-spot waterflood patterns were implemented from 2011 to 2012. These patterns were located in both South East and North West part of Mauddud reservoir with a maximum injection rate of 80 MBWPD. With less than 10% PV water injected as of December 2012, premature water breakthrough was observed in most of the producers. Rapid water breakthrough in Mauddud A (Ba) is attributed to presence of high permeability vugs and layers resulting water cycling and poor sweep in the matrix leaving bypassed oil. Following recommendations from the 2013 partner Peer Assist, the South East and North West waterfloods have been converted from pattern to peripheral with down dip wells providing water injection. Peripheral re-alignment has arrested the production decline, reduced water cut and stabilized the production. Surveillance data such production logs, reservoir saturation logs, noise logs, temperature and tracer data form the basis of understanding waterflood performance. Additionally, an array of analytical tools were used for diagnosis and analysis. Amongst the diagnostic tools, the Y- function helped to understand water cycling and sweep; the modified-Hall plot helped understand high-permeability channel or lack thereof and water-oil-ratio (WOR) gave the clue on fluid displacement. Additional plots such as "X" plot, hydrocarbon pore volume injected vs. recovery, Jordan plot, Cobb sweep plot, Stagg's plot and decline curve analysis were generated to gain insight on the sweep, recovery and remaining moveable oil of the waterflood. Based on the waterflood analysis, a field study was initiated in December 2016 by shutting more than 80% of water injection followed by complete shut-in in September 2017. The motivation was to reduce the water cut, improve production taking advantage of gravity drainage effect of gas injectors located up dip of waterflood areas. The implementation of water injection shut-in is still ongoing in the field and pressure/production performance is being closely monitored. This study underscores the importance of fit-for-purpose surveillance data along with ensemble of modern analytical tools to diagnose and analyze waterflood performance. This understanding also paves the way for much improved learning to take appropriate actions and help devise long-term reservoir management strategy.

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Reservoir Performance Analysis of Eighty-Four Years of Immiscible Gas Injection in a Matured Carbonate Reservoir, Bahrain Field

Hameed

Konwar

Alanaisi

et al. 2022

Day 2 Tue, November 01, 2022

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The Bahrain Oil Field ("Bahrain Field"), wherein the first oil discovery was made in the Gulf region in 1932, is now in a mature stage of development. Mauddud is the major oil-producing reservoir in the Bahrain Field, situated in an anticlinal feature of the middle cretaceous period. This is a highly undersaturated, low-dip, layered, heavily faulted, and preferentially oil-wet reservoir. Crestal gas injection (GI) in Mauddud has continued to be the dominant drive mechanism since 1938, making it the first improved recovery project in the Arabian Gulf region. This paper summarizes the performance of nearly 84 years of gas injection in Mauddud reservoir. Performance-based analysis is carried out using different analytical techniques to determine voidage replacement and maximum gas-cap expansion rate to avoid gas overrunning and injection requirements. Volumetric sweep is estimated using volume of gas injected and gas cycled. Recovery is calculated based on material balance analysis using hydrocarbon pore volume (HCPV), gas injected, free gas-cap volume, and volume of residual oil in gas-cap (VOR). Semilog analysis of free gas/oil ratio (GOR) versus cumulative oil (Np) yields swept pore volume and moveable oil in different areas. Gas management strategy is devised based on wells to be shut-in, cut-off GOR, oil deferred, gas cycling limit, and remediation of high GOR wells with gas shut-off workovers. Optimum number of infill wells is evaluated based on NPV (net present value) for both vertical and horizontal completion. Gas injection gravity drainage is an efficient mechanism in the Mauddud reservoir. Based on gas expansion rate to avoid gas overrunning, maximum GI rate is 652 MMscf/D. The volumetric sweep by gas is around 80%, giving a 50% recovery in gas-invaded areas. Critical gravity drainage oil rate per well is 383 STB/D. The average cycling of gas was 60% initially during 1970's, declined to 50% during 1986 to 2000, and currently increased to over 80%. The cumulative gas cycling is around 70%. Areas B, D, G, and H have the highest remaining mobile oil and should be the focus for infill drilling. A GOR cut-off of 80,000 scf/STB involves 97 wells, resulting in a gas reduction of 200 MMscf/D and an oil rate of 1,600 STB/D. A curtailment of free gas production of 100 MMscf/D will reduce the gas cycling from 87% to 70%. Cased hole horizontal well trial is promising based on workovers of open-hole horizontal well and newly drilled horizontal well trial with cemented liner. The development of Mauddud with a mix of both deviated/vertical and horizontal wells will reduce the number of wells in the tight spacing drilling campaign and provide robust economics. The methodology and analytical techniques described in this paper can be used for performance-based analysis of a large immiscible gas injection project.

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The Development of a Novel Log Based Permeability Transform for a Mature Carbonate Reservoir and its Significance in Explaining the Water Flood EOR Response

Cited by 3 publications

References 3 publications

Nationwide Subsidence in Bahrain Island: Drivers and Implications for Relative Sea-Level Rise

Nationwide Subsidence in Bahrain Island: Drivers and Implications for Relative Sea-Level Rise

Understanding Mauddud Waterflood Performance in a Heterogeneous Carbonate Reservoir with Surveillance Data and Ensemble of Analytical Tools

Reservoir Performance Analysis of Eighty-Four Years of Immiscible Gas Injection in a Matured Carbonate Reservoir, Bahrain Field

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