A generalized scaling equation to predict asphaltene precipitation during precipitant dilution, natural depletion, water injection and gas injection

The purpose of the three experiments described in this paper is to investigate the efficiency of secondary andtertiary gas injection in fractured carbonate reservoirs, focusing on the effect of equilibrium gas,re-pressurization and non-equilibrium gas. A weakly water-wet sample from Asmari limestone which is the mainoil producing formation in Iran, was placed vertically in a specially designed core holder surrounded withfracture. The unique feature of the apparatus used in the experiment, is the capability of initializing the samplewith live oil to obtain a homogeneous saturation and create the fracture around it by using a special alloy whichis easily meltable. After initializing the sample, the alloy can be drained from the bottom of the modified coreholder and create the fracture which is filled with live oil and surrounded the sample. Pressure and temperaturewere selected in the experiments to give proper interfacial tensions which have been measured experimentally.Series of secondary and tertiary gas injection were carried out using equilibrium and non-equilibrium gas.Experiments have been performed at different pressures and effect of reduction of interfacial tension werechecked by re-pressurization process. The experiments showed little oil recovery due to water injection whilesignificant amount of oil has been produced due to equilibrium gas injection and re-pressurization. Results alsoreveal that CO2 injection is a very efficient recovery method while injection of C1 can also improve the oilrecovery.

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Laboratory Investigation of Permeability Impairment Caused by Asphaltene Precipitation during Screening for Gas-Injection Enhanced Oil Recovery and Pressure Change in a Major Gulf of Mexico Field

SPE Journal ◽

10.2118/200429-pa ◽

2021 ◽

pp. 1-21

Author(s):

M. R. Fassihi ◽

E. Turek ◽

M. Matt Honarpour ◽

D. Peck ◽

R. Fyfe

Keyword(s):

Gulf Of Mexico ◽

Gas Injection ◽

Rock Surface ◽

Permeability Reduction ◽

Test Results ◽

Asphaltene Precipitation ◽

The Core ◽

Asphaltene Deposition ◽

Core Permeability ◽

Permeability Impairment

Summary As part of studying miscible gas injection (GI) in a major field within the Green Canyon protraction area in the Gulf of Mexico (GOM), asphaltene-formation risk was identified as a key factor affecting a potential GI project. The industry has not conducted many experiments to quantify the effect of asphaltenes on reservoir and well performance under GI conditions. In this paper we discuss a novel laboratory test for evaluating the asphaltene effect on permeability. The goals of the study were to define the asphaltene-precipitation envelope using blends of reservoir fluid and injection gas, and measure permeability reduction caused by asphaltene precipitation in a core under GI. To properly analyze the effect of GI, a suite of fluid-characterization studies was conducted, including restored-oil samples, compositional analysis, constant composition expansion (CCE), and differential vaporization. Miscibility conditions were defined through slimtube-displacement tests. Gas solubility was determined through swelling tests complemented by asphaltene-onset-pressure (AOP) testing. The unique procedure was developed to estimate the effect of asphaltene deposition on core permeability. The 1-ft-long core was saturated with the live-oil and GI mixture at a pressure greater than the AOP, and then pressure was depleted to a pressure slightly greater than the bubblepoint. Several cycles of charging and depletion were conducted to mimic continuous flow of oil along the path of injected gas and thereby to observe the accumulation of asphaltene on the rock surface. The test results indicated that during this cyclic asphaltene-deposition process, the core permeability to the live mixture decreased in the first few cycles but appeared to stabilize after Cycle 5. The deposited asphaltenes were analyzed further through environmental scanning electron microscopy (ESEM), and their deposition was confirmed by mass balance before and after the tests. Finally, a relationship was established between permeability reduction and asphaltene precipitation. The results from the asphaltene-deposition experiment show that for the sample, fluids, and conditions used, permeability is impaired as asphaltene flocculates and begins to coat the grain surfaces. This impairment reaches a plateau at approximately 40% of the initial permeability. Distribution of asphaltene along the core was measured at the end by segmenting the core and conducting solvent extraction on each segment. Our recommendation is numerical modeling of these test results and using this model to forecast the magnitude of the permeability impairment in a reservoir setting during miscible GI.

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Challenges and Lesson Learnt of 1st IWAG Implementation in a Mature Oil Field, East Malaysia

10.2523/iptc-21332-ms ◽

2021 ◽

Author(s):

Kok Liang Tan ◽

Sulaiman Sidek ◽

Syakirin M. Nazri ◽

Haziqah Hamzah

Keyword(s):

Performance Test ◽

Gas Injection ◽

Water Injection ◽

Pressure Gauge ◽

Management Plan ◽

Injection Rate ◽

Oil Field ◽

Cycle Duration ◽

Fluid Temperature ◽

Tertiary Recovery

Abstract Immiscible Water Alternating Gas (iWAG) scheme was adopted in Echo field, offshore Sarawak Malaysia, to increase recovery factor of the matured oil reservoir after more than two (2) decades of peripheral water injection. It was implemented through four (4) horizontal wells located at reservoir’s eastern and western flanks. Since the commencement of iWAG injection, multiple challenges occured interrupting the stable injection that halting the success of this integrated mega scale project. It started with prolonged iWAG performance test run due to surface constraint, measurement and well issues on executing switching test, followed with low injectivity during switching operation. Subsequently, injectivity issues occured in the gas phase after several injection cycles. In addition to that, injector wells facing high downtime due to surface facilities and well integrity issues, causing low injection rates and unavailability to meet cycle volume within the stipulated duration. Reactivation of iWAG benefiter wells also prove to be challenging due to wells have been idle for a long time and multiple interventions required to revive the well. Injection data for both gas and water phase were analysed to improve iWAG operating procedure and understand the wells performance. INJ-J2 was installed with temporary pressure gauge during the water to gas switching, while the other two (2) wells are equipped with Permanent Downhole Gauge (PDG) to monitor the well injectivity. Application of non-intrusive flowmeter was also proven useful in calibrating the Flow Transmitter (FT) for both water and gas injectors, ensuring the accuracy and precision in the water and gas injection measurement. Besides that, fluid temperature trending was referred to validate on the meter measurement. Low injection rate compared to original plan were reviewed with the Reservoir Management Plan (RMP). Several approaches are implemented in order to achieve the iWAG RMP target and idle well reactivation. Analysis of injection data showed that gas injectivity issue occurred after the water to gas switching cycle. Injectivity improves slightly after long duration of continuous gas injection and applying higher Tubing Head Pressure (THP), unfortunately some wells remain with low injectivity because of insufficient discharge pressure to push the water from the near-wellbore deep into the reservoir to improve injection. Low injection rate issue is mitigated by extending injection cycle duration in order to meet the RMP cycle volume. Besides that, wells are normally injected with higher injection rate to cater for the high downtime. Both gas and water injection are balanced to ensure that the wells reached their cycle volume at similar duration. With limited new field discovery by the Operator, tertiary recovery on the mature field is inevitable. However, there is less implementation of iWAG in offshore field. Through this paper, authors wish to provide insights and lesson learnt for others when planning for iWAG tertiary recovery, taking account of various challenges faced.

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Innovation and instrumentation in CO2 monitoring wells for reservoir surveillance and advanced diagnostics

The APPEA Journal ◽

10.1071/aj20188 ◽

2021 ◽

Vol 61 (2) ◽

pp. 530

Author(s):

Paul Barraclough ◽

Mohamad Bagheri ◽

Charles Jenkins ◽

Roman Pevzner ◽

Simon Hann ◽

...

Keyword(s):

Carbon Capture ◽

Gas Injection ◽

Water Injection ◽

Carbon Capture And Storage ◽

Injection Well ◽

Fibre Optics ◽

Monitoring Wells ◽

Co2 Monitoring ◽

Optic Systems

In 2015, CO2CRC Ltd embarked on an ambitious plan to field test innovative technologies to monitor a CO2 plume injected into a saline aquifer with a view to address many of the economic and environmental concerns frequently associated with commercial carbon capture and storage project’s long-term monitoring programs (Jenkins et al. 2017). It was called the Otway Stage 3 Project and it was focused on testing the technologies of seismic and downhole pressures applied in unique ways to monitor an injected plume of approximately 15000 tonnes as it developed and migrated in the subsurface. To achieve this goal, five new wells were drilled at CO2CRC’s Otway International Test Centre – one dedicated to injection (drilled in 2017) and the remaining four wells (drilled in 2019) were used for monitoring purposes. Each monitoring well and the gas injection well, were outfitted with fibre optic systems installed and cemented outside the casing (specifically for seismic monitoring) and with pressure gauges installed at the reservoir depth. The challenge of the installation was to install fibre optics outside of the casing, cement them in place securely and to perforate the wells without damaging the fragile TEF bundles. While the installation of the pressure gauges in the injection well was a conventional in-tubing gauge mandrel, the installation in the monitoring wells, which were to be used for water injection as well as pressure monitoring, used a less conventional deployment method, where the gauges were instead installed using a more economic and flexible approach by suspending the gauges from the wellhead via a hanger system. This not only ensured continuous offline monitoring of the downhole well pressures and temperatures, but also facilitated future well operations by simple wireline retrieval and deployment of the gauge, forgoing the need for a workover rig. The various systems were commissioned over the period of March–June 2020 and were in full operation in the second half of 2020 – all successfully operating and acquiring baseline data remotely as designed. The Stage 3 Project commenced gas injection operations in December 2020 and data acquisition using the innovative systems have commenced successfully.

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