Identification of Remaining Reserves Using Pulsed Neutron Logging for Pressure Determination Behind Casing in Mature Gas Condensate Reservoirs

Gray, R.; Smith, Emma; Parsa, Ali; Kim, Yonghwee; Odusi, Gbolahan

doi:10.2118/196090-ms

Cited by 4 publications

(1 citation statement)

References 5 publications

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“…In 2017, Zhou et al introduced Monte Carlo model digital processing technology to correct the influence of complex measurement environment and studied the application of RPM-C Gasview reservoir evaluation technology in Tarim oil field [12]. In 2019, Gray et al used a combination of pulsed neutron logging data and a Monte Carlo forward modeling model to estimate the gas pressure behind the casing and then evaluated the depletion of the condensate gas reservoir [13]. In 2020, Rose et al studied a method for calculating reservoir gas pressure using pulsed neutron logging data [1].…”

Section: Introductionmentioning

confidence: 99%

Study on Monitoring Reservoir Gas Density by Pulsed Neutron Logging

Chen

Dang

Cai

et al. 2023

International Journal of Energy Research

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In mature multilayer gas reservoirs, it is a common problem to evaluate whether a potential reservoir is still productive after casing. Monitoring of unproduced or developing gas formations can guide production action plans. Intervention in unperforated zones with high gas density can increase gas production, whereas intervention in zones with low gas density is uneconomical. An RPM instrument stratum model was established by using the Monte Carlo method in this study. The model was used to simulate the response characteristics of pulsed neutron logging in a sandstone reservoir with 100% gas saturation to different reservoir gas densities, formation porosity, and shale content. The data obtained from the simulation were interpolated to construct a capture gamma ratio plate and a nonbounce gamma ratio plate. Using the constructed chart, the gas density of the reservoir can be quantitatively calculated, and then, the recovery value of the potential gas layer can be evaluated.

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Section: Introductionmentioning

confidence: 99%

Study on Monitoring Reservoir Gas Density by Pulsed Neutron Logging

Chen

Dang

Cai

et al. 2023

International Journal of Energy Research

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Pressure Depletion Delineation for a Deep Gas Condensate-Producing Well in the North Sea

Kim,

Gray,

Odusi

2023

Day 3 Wed, October 18, 2023

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Understanding the current pressure of unperforated gas reservoirs is critical for field development. Perforation of depleted reservoirs results in low hydrocarbon production, unwanted water production, or no flow. Thus, a through-casing well-based reservoir pressure surveillance is essential before perforating the target zones to assess if pressure depletion occurs due to the production of connected reservoirs from offset wells. Pulsed neutron (PN) logging in wells filled with produced gas can reduce some measurements’ formation sensitivity. For example, ratio-based measurements required for gas saturation and pressure depletion analysis using inelastic gamma-ray count rates can be particularly affected when wellbores are gas-filled. As a solution, a sleeved-PN well logging technique was developed to delineate pressure depletion in cased gas-producing wells. The pulsed neutron source and gamma-ray detectors of the sleeved-PN tool are covered with a layer of hydrogen-rich material, such as fiberglass, thereby improving the measurements’ formation sensitivity compared to ones from a regular PN tool in a gas-filled wellbore. The pressure depletion evaluation workflow includes nuclear measurements from a sleeved-PN tool, the Monte Carlo N-Particle (MCNP) method-based forward modeling of tool responses, and an iterative analysis algorithm. We deployed a sleeved-PN logging tool in a gas condensate-producing well in the North Sea. The well was produced from deeper Triassic sands with a section of Jurassic sand bodies above which are not perforated and of uncertain depletion. During PN logging, the wellbore was filled with gas from the deeper perforated sands. Pressure depletion analysis was performed using three key measurements: inelastic and capture gamma-ray count rate ratios and a macroscopic thermal neutron capture cross-section (formation sigma). Each measurement revealed distinctive characteristics; therefore, comparing these measurements integrated with forward modeling responses allowed for determining reservoir pressure depletion. Accurate MCNP modeling was a crucial factor in the pressure depletion evaluation. Furthermore, the current in-situ gas density estimation was based on a series of MCNP modeling results. An iterative method of comparing measured and modeled data with reference to original water saturation was used to calculate the current gas density. The analysis showed indications of pressure depletion in the lower sand section but not in the upper formation. Ratio-based PN measurements were effective in indicating depletion. Formation sigma was practical to compute the current water saturation as it is relatively insensitive to changes in reservoir pressure and gas density. Evaluating pressure depletion before perforating sands in gas-producing wells, especially when gas is present in the borehole, is challenging. However, advances in PN logging technique and an innovative data analysis method enabled cost-effective monitoring of formation pressure in a cased-hole environment and enhanced confidence in reservoir management decision-making.

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Formation Gas Quantification in the Z-Field Niger Delta Using Multidetector Pulsed Neutron Well Logging Technology

Akagbosu,

Kim,

Adesokan

2024

SPE Nigeria Annual International Conference and Exhibition

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The quest for optimal gas detection and quantification in Niger Delta regions for sustainable energy development necessitates advanced technologies. This paper explores a multidetector pulsed neutron well logging technology with improved formation gas sensitivity for precisely characterizing reservoir fluids and estimating gas saturation in a freshwater environment. This innovative method is applicable to tight porosity and low water salinity formations, which are historically challenging conditions for accurate saturation analysis with conventional pulsed neutron logging applications. This technology encompasses (1) a pulsed neutron generator that creates high-energy neutrons that interact with formation nuclei and create induced gamma rays and (2) three gamma-ray detectors and an electronics system that records induced gamma rays based on the gamma-ray energy level and arrival time. In addition, forward modeling of tool responses is a critical component. Monte Carlo N-Particle (MCNP) modeling simulates the three-detector pulsed neutron tool’s gas-sensitive log responses. The predicted MCNP models are incorporated into the saturation analysis workflow to identify and quantify the formation gas saturation considering reservoir fluid properties, lithologies, well completions, and cement densities. A case study demonstrated the use of multidetector pulsed neutron well logging technology for quantitative formation gas evaluations of cased-off reservoirs in the Z-field Niger Delta. This contributes to the use of gas resources for sustainable energy development in Africa.

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Identification of Remaining Reserves Using Pulsed Neutron Logging for Pressure Determination Behind Casing in Mature Gas Condensate Reservoirs

Cited by 4 publications

References 5 publications

Study on Monitoring Reservoir Gas Density by Pulsed Neutron Logging

Study on Monitoring Reservoir Gas Density by Pulsed Neutron Logging

Pressure Depletion Delineation for a Deep Gas Condensate-Producing Well in the North Sea

Formation Gas Quantification in the Z-Field Niger Delta Using Multidetector Pulsed Neutron Well Logging Technology

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