Wellbore monitoring techniques are proving to be significant in reservoir management and intervention design, particularly in unconventional fields where fluid flow behavior is not very well understood. Distributed temperature sensing (DTS) technology allows for an estimation of zonal flow rates in the entire well as a function of time during hydraulic fracturing, as well as during the production phase.In this work, a novel transient thermo-hydraulic model that includes fluid transport and thermal coupling and simulates fluid flow and temperature in both the wellbore and reservoir is presented. Real DTS data from a hydraulic fracturing operation in a low-permeability basin in west Texas has been inverted using this model. Flow allocation based on the thermohydraulic model is presented. It was found that the reservoir heterogeneity, and hence the zonal flow rates, can be accurately obtained based on temperature and pressure data from the well.Most of the steady-state DTS data inversion models are typically applicable to production scenarios, where the transient in temperature has vanished. Injection operations, such as in fracturing where the temperature does not achieve a steady-state during the injection stage, require a transient model that can capture the initial-time effects. Also, some of these models fail to include the Joule-Thomson effect, and this leads to an incorrect flow allocation. The thermo-hydraulic model developed in this work includes both the Joule-Thomson and transient effects. It can be applied to non-reactive fluid injection during stimulation operations, such as matrix acidizing and fracturing. In particular, application of the model for fluid distribution before, during, and post-fracturing provides an estimate of the efficiency of fracturing stages.
The latest well completions developments for extended-reach wells include advanced techniques to improve the effectiveness of production and optimization solutions to achieve sustainable well production. Monitoring systems installed during the completion use real-time distributed temperature sensing (DTS), distributed acoustic sensing (DAS), and downhole gauge data to obtain better reservoir insight throughout the life of the well. This enables informed decision making to achieve optimal well production and gas injection. Permanent downhole gauges (PDGs) with dual sensors (tubing + tubing) are installed, along with hybrid cable as part of the upper completion string. The hybrid cable has an electrical conductor and two fiber-optic lines for DTS and DAS measurements. The cable is clamped onto the tubing at each coupling and passes through the upper completion subassemblies, which include gas lift mandrels (GLMs) and tubing-retrievable safety valves (TRSVs). An intermediate completion is run before the upper completion, which comprises a two-trip permanent packer and remote actuated barrier device (multicycle). Completions monitoring with hybrid cables provides an advantage over conventional gauge-only systems, with only a slight increase in completion costs. Using a single cable provides more run-in-hole (RIH) efficiency, fewer lines to manage, and a smaller equipment footprint. PDG data are used by production engineers, field development personnel, and subsurface personnel to determine pressure drawdown and optimize surface production choke size. Distributed fiber-sensing technology determines the effectiveness of gas lift operations to optimize injection rates, which effectively optimizes pumping rates and flow from surface. Fiber-sensing technology also helps identify tubing and annulus leaks, monitor the health of the completion during the life of the well, and minimize wellbore damage. This type of completion has been installed successfully in 64 wells (60 production and 4 injection), and all systems are operational with data accessible from all wells. This approach benefits the industry by highlighting best practices, providing advanced technology options for evaluating data and reservoir productivity, and providing completion and drilling effectiveness for extended deep-reach wells.
Injection profile enhancement has been one of the primary objectives for an operator in Kuwait. Stimulation interventions in injector wells directly affect the enhancement of oil recovery in producer wells. This paper presents the application of a verifiable stimulation intervention in a water injector well to help achieve the operator's objectives. The intervention presented several challenges. There was limited information available for the newly drilled carbonate formation under consideration in the Greater Burgan Field. Additionally, the fiberglass well tubing required significant attention before running in hole (RIH) with coiled tubing (CT). A high concentration of H2S was identified in Formation A; therefore, gas returns were also a potential issue. This paper discusses the methods used to help address these challenges. During this case study, real-time fiber-optic cable CT (RTFOCT) technology was applied in the fiberglass tubing injector well to determine initial well injection profile and adjust treatment accordingly. This technology includes a fiber-optic cable integrated into the CT pipe and a modular sensing bottomhole assembly (BHA). RTFOCT technology allows for rigless operations and performs interval diagnostics, stimulation treatment, and evaluation in a single CT run. During this case study, the well injectivity increased by more than 100%. Diagnostics and evaluation were performed by analyzing the well thermal profile using fiber-optic distributed temperature sensing (DTS). The BHA helped ensure accurate fluid placement during the treatment using real-time pressure, temperature, and depth-correlation sensors. The RTFOCT technology provided real-time downhole information that was used to analyze reservoir parameters, help ensure accurate fluid placement, and enable quick and smart decisions regarding the stimulation treatment stages based on the fluid intake in different zones. During injection, the heterogeneous fluid flow became homogeneous along the interval confirmed with the thermal-hydraulic model (THM). This helped reliably complete the intervention operations and delay possible water breakthrough in the producer wells and extended reservoir recovery.
Increasing water cut and well integrity are currently major concerns, particularly in mature fields. Excessive water production can detrimentally affect the profitability of hydrocarbon-producing wells if not controlled properly. This paper describes a successful zonal isolation case study in a dual-string completion well with well integrity challenges and variable permeability intervals using a modified organically crosslinked polymer (m-OCP) and coiled tubing (CT)-assisted real-time temperature sensing for effective placement and post-operation evaluation. The m-OCP system is a combination of a thermally activated, organically crosslinked polymer and particulate material for leakoff control to help ensure shallow matrix penetration. It is acid resistant, H2S tolerant, has controlled penetration, and is easy to clean up using a rotating wash nozzle. The setting time can be accurately predicted with simple laboratory tests. These characteristics make this system the preferred choice compared to the traditional cement squeeze method that is both time consuming and exorbitant. Diagnostic services delivered by CT-conveyed fiber-optic distributed temperature sensing (DTS) that add real-time capabilities to monitor well integrity assess reservoir performance and visualize treatment efficiency. Using real-time diagnostic services, tubing integrity was confirmed, and the treatment was placed in the same run, helping eliminate the possibility of an undesired leakoff. After allowing the setting time, a successful pressure test or post-cleanout DTS (in case pressure test is not feasible) was used to establish the reliability of this method. The first attempt was made on Well A of the field; however, isolation was successful using m-OCP and conventional CT. Operation execution and production recovery took more time than planned because of the uncertainty concerning well integrity in the dual-string completion and lost circulation in the depleted reservoir, which affected the economic deliverability of the operation. The major challenges with Well B of the same type in the same field remain the same. Thus, as part of lessons learned from the previous intervention, diagnostic services were chosen for a real-time evaluation of the completion to review well integrity and accurately place the optimized treatment, thereby helping improve overall results in the most time-saving and lucrative manner. The successful isolation of the water-producing zone/perforations in the southeast Kuwait field using m-OCP and CT-assisted real-time DTS to review well integrity can be considered a best practice for addressing similar challenges globally.
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