Macki, Ali Al (Petroleum Development Oman) | Salmi, Albashir Al (Petroleum Development Oman) | Duggan, Timothy (Petroleum Development Oman) | Delgado, Eduardo (Petroleum Development Oman) | Kechichian, Jackie (Petroleum Development Oman) | Busaidi, Hamood Al (Petroleum Development Oman) | Azri, Nasser Al (Petroleum Development Oman)
Well integrity is one of the highest operational risks for E&P companies across the industry. As such, well integrity concerns are high priority for operational excellence. Electromagnetic Corrosion Logs have been more frequently acquired as Cased-hole logging services enabling the quantification of multi-barrier well integrity. Due to ease of data acquisition through logging operations and the ability to model remaining metal thickness per-barrier from acquired surveys, demand for Electromagnetic Corrosion Logs has been sharply growing across the industry. Electromagnetic Corrosion Logs can compliment conventional integrity tests and can be used for well integrity compliance where business-critical decisions are accordingly made.
Electromagnetic corrosion logs are run more frequently across assets to investigate time-lapse per-barrier integrity status for multi-barrier systems (multiple concentric tubulars). Degradation in barrier integrity in operating wells present integrity risks. Harsh operating environments during production/injection, sour environments, life-time wear and tear, and shallow aquifers all affect wellbore integrity in the form of internal and external metal loss. Electromagnetic Corrosion Logs are currently reported to be capable of quantifying total remaining metal per-casing (separately) up to three barriers.
In 2016, a yard test was conducted in Oman to assess the limitations of different Electromagnetic corrosion tools. The test consisted of multi-barrier concentric oil-field tubulars of different sizing and set-up. Four tubular set-ups (simulating routine well completions) were constructed with man-made "corrosion" features to assess raw, processed and interpreted Electromagnetic Corrosion logs. The man-made features included defects of various shapes and configurations distributed axially and longitudinally as well as machined thickness-loss areas with precise thresholds. Multiple service providers with different tools and configurations were requested to acquire corrosion logs through the yard test "completions."
This paper investigates Electromagnetic Corrosion Log technology. It illustrates the physics, practice, and applied technology scope of Electromagnetic Corrosion Logs gathered from the yard test and multiple surveys in Petroleum Development of Oman (PDO). The outcome is improved awareness of operational windows, tool resolution and sensitivities, detection capability, data QC and analysis, processing, and modeled thickness outputs. Some discussion is made around the limitation of Electromagnetic Corrosion Logs and the uncertainty in thickness estimation, and recommendations for this technology's scope for application.
Miqrat is a complex clastic deep tight gas reservoir in the North of the Sultanate of Oman. The Lower unit of the Miqrat formation is feldspatic sand characterized by low permeability not exceeding 0.1 mD and porosity up to 12 %. Based on results of the appraisal campaign of Field X, it contains significant volume of gas. However the production test data after fraccing showed mixed results. The objective of this study was to explain the production behavior and identify the sweetspot area for further development.
Understanding the reason of possible overestimation of log derived Hydrocarbon saturation is important. Thus the interpretation of conventional and special logs was revisited. In parallel, all the available core data including SCAL and thin sections were scrutinized. Besides, the analysis of hydraulic fracture propagation, well tests, cement quality, PLT including Spectral Noise Log was performed. The wells were subdivided into categories according to their production results: wells producing no water wells with water channeling from the water leg of Middle Miqrat wells with transition zone intervals with 2 phase inflow of water and gas.
wells producing no water
wells with water channeling from the water leg of Middle Miqrat
wells with transition zone intervals with 2 phase inflow of water and gas.
Based on the integrated analysis, extend of the gas and transition zones was established, and the location of future wells optimized. From the Spectral Noise log and Temperature data, water crossflow/channeling from Middle Miqrat was identified in 2 wells, either because of broken thin sealing shale above Lower Miqrat or due to poor cement quality. The sweetspot area with commercial production was mapped. Substantial gas volumes have been unlocked. Besides, an explanation of the uncertainty in log derived saturation was suggested. Core plugs and thin sections revealed presence of partially filled vugs, which is not a typical case in a clastic environment. The origin of this porosity is puzzling and likely due to dissolution of early diagenetic nodules. The rock with poorly connected vugs has high resistivity even if it is water bearing. The review of capillary pressure data revealed that the transition zone could exceed 100 m. This finding is consistent with the interpretation from well tests.
The most practical implication of the current study potential of Lower Miqrat is unlocked. The integration of Open hole and cased hole logs and the additive information from Spectral Noise log for channeling/crossflow identification is shown. Presence of vuggy-like porosity in clastic sections and the impact of isolated vugs on log derived Saturation is demonstrated.
First and secondgeneration drilling microchipsare compared side by side on design architecture, system components, sensors, output signal, build materials etc. Temperature microchips were field tested in an on-shore well. From the 20 deployed microchips, 6 passed through the bit nozzles and survived the drilling process without causing any downtime to the operation. The data recorded by different microchips showed excellent consistency over the downhole part of the trip, from inside of the drill pipe up the annulus to the surface. This is the first time that a drilling microchip was successfully deployed while drilling, and a complete set of data recorded throughout the entire trip from drill pipe, to the annulus, all the way to the flow line and shale shaker. The consistent results from the microchip provide valuable information for a wide range of drilling activities.
An infill drilling campaign in offshore Myanmar was facing challenges to accommodate well intervention activity in order to achieve additional production targets; therefore, there was a need to search for an alternative, cost-effective solution in the current environment. A well with potential behind-casing opportunity was identified, and an innovative solution was proposed using coiled tubing (CT) fiber-optics real-time telemetry combined with the latest high-power battery cartridge technology to convey a tool capable to identify the reservoir saturation and conclusively detect the bypassed zones.
As a result of rig-up constraints, a standalone wireline unit could not be used to deploy the reservoir saturation tool on the selected well. The innovative solution was to convey the reservoir saturation tool using CT fiber-optics real-time telemetry along with the latest-technology high-power battery cartridge system, allowing real-time logging with CT, including additional safety precautions and radiation hazard controls while using the pulsed neutron generator device.
The intervention was performed concurrently with drilling operations on an adjacent well. A major effort was put in place to plan and execute this operation, especially because open well deployment was needed to address the rig-up height issue while doing the job below the rig floor; this was in addition to the extensive HSE risk mitigation for using the radioactive pulsed neutron generator device. The well was killed successfully, and the reservoir saturation tool was conveyed with CT to the target zone where two logging passes were made. Data were then sent for interpretation, and the CT was pulled back to surface after confirmation of data quality. As a result, the operator obtained conclusive data, and the decision was made to shut off the existing perforated zones and perforate the identified BCO. The simultaneous intervention and drilling operations, reduced footprint, and the additional production from this well saved the operator up to USD 2 million. With the integration of CT and wireline technologies and the introduction of a novel battery system for high-consumption logging tools such as the reservoir saturation tool, the operator efficiently and cost-effectively acquired data without nonproductive time (NPT) or compromising safety during operations.
An innovative and first-time operation in the entire region (Asia), the use of CT fiber-optics real-time telemetry combined with the latest high-power battery cartridge technology to deploy the reservoir saturation tool overcame operational challenges and enabled successful identification of the bypassed zone. The combination of these technologies can benefit other regions and other similar operations.
The definition of the actual net pay is one of the most important parameter for a comprehensive dynamic petrophysical reservoir characterization. In heterogeneous reservoirs, well test interpretation lacks a direct link with the real flowing thickness of the reservoir units and this represents the major cause of inaccurate permeability estimation. Usually production logging can represent the conventional way to collect this kind of information; however, in offshore deep water wells, these operations entail risks, costs and time.
The paper deals with a robust dynamic characterization approach based on a continuous temperature measurement performed during the whole well test operations in a deep water gas well. This novel technology provides a mapping of the flowing contributions thanks to temperature sensors integrated on the perforation guns overcoming risks and costs of a standard production logging tool (PLT) acquisition.
An accurate openhole logs static reservoir characterization was performed to drive the detailed flow allocation in the tested heterogeneous reservoir. In particular, resistivity invasion profiles, wireline formation test data and advanced nuclear magnetic resonance (NMR) interpretation provided a detailed petrophysical background on which a quantitative formation thermal evaluation was achieved. The time-lapse temperature analysis during the different well test periods (clean-up, draw-downs and final build-up) allowed the estimation of continuous logs of net pay, zonal contribution and effective permeability.
The application of this methodology, as well as mitigating time, risks and costs, is a driver to optimize well completion strategy and to calibrate the 3D reservoir model for a correct reserves allocation.
One of the most challenging issues to be addressed in reservoir characterization is the simultaneous definition of the static and dynamic rock properties in order to optimize the well completion and accordingly maximize hydrocarbon production.
While the estimation of static petrophysical properties comes from ad-hoc interpretations of well log data, the most common and practical way to collect information about dynamic downhole well behavior is Production Logging (PLT). This kind of data acquisition is commonly carried-out after the well test acquisition in order to provide an accurate contributing net pay value. Some static-to-dynamic frameworks have shown successful results (see more details in Pirrone et al, 2016) and have been also fruitful for the interpretation of what controls effective permeability in complex scenarios.
The dynamic characterization and the description of fluid flow behavior at well location are critical steps for production optimization and reservoir modeling purposes. The conventional approach makes use of well test data interpreted by adopting appropriate analytical models aimed, in particular, at permeability evaluation and flow regime identification. In complex reservoir scenarios, the standard well test interpretation lacks a direct link with the actual flowing thickness of the reservoir rock and this represents the major cause of inaccurate permeability estimations. Moreover, an a-priori knowledge of fluid flow path through the porous medium and around the wellbore is one of the most desired targets but, at the same time, one of the most challenging issues to be addressed.
This paper deals with a novel dynamic characterization approach that mainly integrates well test data and spectral noise logging. The latter, with its high-resolution noise pattern recognition in a wide frequency range, can provide valuable information of the fluid flow behavior in the near wellbore region in order to locate the active units and to describe the origin and the character of the flow (through mesopores, macropores, fractures, behind-casing channels and completion elements).
The added value of the methodology is demonstrated by means of a study performed on three wells drilled in a Cretaceous carbonate reservoir. The accurate estimation of the net-pay flowing thickness, after a fit-for-purpose modeling of noise data, revealed the subsequent robust estimation of effective permeability and different scenarios with respect to those based on standard approaches. Then, the integration of quantitative spectral noise analysis, pressure transient tests, production logging data, and advanced nuclear magnetic resonance log interpretation completed the picture of the flow regime through the pore-space. In turn, the results represent a critical input for the dynamic reservoir model, and a fruitful driver to optimize commingled completions or required workovers.
The deep understanding of fluid movement from sandface to surface is a critical aspect in production optimization and reservoir modeling studies. According to conventional approaches, the actual dynamic characterization of a well usually comes after production logging tool (PLT) data interpretations and/or well test (WT) analyses.