Screening and assessing the conditions for effective oil recovery enhancing techniques application for hard to recover high-water cut reserves

For the conditions of deposits in Jurassic and Paleozoic terrigenous reservoirs of the Sherkalinsky trough and Shaimsky swell of Western Siberia, a criterion analysis and screening of enhanced oil recovery techniques used in the fields of the West Siberian oil and gas province were carried out. For various groups of oil fields, a set of the most effective technologies for the development of residual hard-to-recover reserves of flooded fields has been proposed. The areas for effective application of the selected techniques for deposits introduced into development within the considered tectonic-stratigraphic elements are determined. The areas determination was carried out on the basis of 19 parameters characterizing the geological-physical and physical-chemical properties of formations and fluids, as well as the maximum and minimum values of the canonical discriminant functions determined by the situational map. Based on the numerical modeling of oil recovery processes, a forecast of an increase in the final oil recovery factor was made for five facilities-field test sites of the selected groups of facilities. Keywords: hard-to-recover reserves; terrigenous reservoirs; factor analysis; enhanced oil recovery techniques; numerical modeling; criterion analysis.

Response to the Variation of Clay Minerals During ASP Flooding in the Saertu Oilfield in the Songliao Basin

In this paper, the variation of clay minerals and their influence on reservoir physical properties and residual oil before and after ASP flooding are analyzed. The results show that the total amount of clay minerals in reservoirs decreases after ASP flooding in the ultra-high-water-cut-stage reservoirs of the Naner Zone in the Saertu Oilfield, Songliao Basin. Therein, the illite content reduces, while the content of illite smectite mixed-layer and chlorite increases. The content of kaolinite varies greatly. The content of kaolinite decreases in some samples, while it increases in other samples. The clay minerals block the pore throat after ASP flooding. As a result, the pore structure coefficient and the seepage tortuosity increase, the primary intergranular pore throat shrinks, and the pore–throat coordination number decreases. Nevertheless, the dissolution of clay minerals reduces the pore–throat ratio and increases porosity and permeability. The variation of clay minerals after ASP flooding not only intensifies the reservoir heterogeneity but also affects the formation and distribution of residual oil. The residual oil of the oil–clay mixed adsorption state is a newly formed residual oil type related to clay, which accounts for 44.2% of the total residual oil reserves, so it is the main occurrence form of the oil in reservoirs after ASP flooding. Therefore, the exploitation of this type of residual oil has great significance to enhance the oil recovery in ultra-high-water-cut-stage reservoirs.

Diagnosing High Water Production in Kalama Field, Niger Delta

Produced water is water trapped in underground formations that is brought to the surface along with oil or gas. It is by far the largest volume by-product or waste stream associated with oil and gas production especially in brown fields. Management of produced water present challenges and costs to operations. In this paper, the possible causes, effects and solutions of high water-cut is being investigated in some production oil wells in Niger Delta, using Kalama field as a case study. Diagnostic and performance plots were developed in order to determine the source of water as well as to evaluate the impact of excess water production on oil production and in field economics in general. Results obtained from the diagnostic plots showed the possible sources of water production are channeling behind casing and multi-layered channeling. The recommended remediation is cementation through a workover operation. Also, a concise step to be taken for identifying excess water was also developed in this work to effectively control excess water production in oil producing wells.

A Successful Application of Continuous Pack-Off Technology to Water Shutoff Recompletion for High-WCT Gravel-Packed Horizontal Well

Objectives/Scope Controlling the excessive water production from the high water cut gravel packing horizontal well is a challenge. The approach which uses regular packers or packers with ICD screens to control the unwanted water does not function well. This is mainly because of the length limitation of packers which will make the axial flow resistance insufficient. Methods, Procedures, Process In this paper, a successful case that unwanted water is shutoff by using continuous pack-off particles with ICD screens (CPI) in the whole horizontal section in an offshore oilfield of Bohai bay is presented. The reservoir of this case is the bottom-water high viscosity reservoir. The process is to run 2 3/8" ICD screen string into the 4" screen string originally in place, then to pump the pack-off particles into the annulus between the two screens, and finally form the 360m tightly compacted continuous pack-off particle ring. Results, Observations, Conclusions The methodology behind the process is that the 2-3/8" ICD screens limit the flow rate into the pipes as well as the continuous pack-off particle ring together with the gravel ring outside the original 4" screens to prevent the water channeling into the oil zone along the horizontal section. This is the first time this process is applied in a high water cut gravel packed horizontal well. After the treatment, the water rate decreased from 6856BPD to 836.6BPD, the oil rate increased from 44BPD to 276.8BPD. In addition, the duration of this performance continued a half year until March 21, 2020. Novel/Additive Information The key of this technology is to control the unwanted water by using the continuous pack-off particles instead of the parkers, which will bring 5 advantages, a) higher efficiency in utilizing the production interval; b) no need to find the water source and then fix it; c) the better ability to limit the axial flow; d) effective to multi-WBT (water break though) points and potential WBT points; e) more flexible for further workover. The technology of this successful water preventing case can be reference to other similar high water cut gravel packed wells. Also, it has been proved that the well completion approach of using CPI can have good water shutoff and oil incremental result. Considering the experiences of historical applications, CPI which features good sand control, water shutoff and anti-clogging is a big progress compared to the current completion technologies.

Strategies to Mitigate the Challenges of Short Circuiting in Waterflood Reservoirs with Tracers: A Case Study

Water short circuiting leading to early, sudden and massive water breakthroughs in producer wells has been a lingering concern to oil operators for many years. Unfavorable mobility ratio leading to viscous fingering, horizontal wells exhibiting ‘the heel-toe effect’ and fields with fracture-fault activities are more prone to these kinds of unwanted water breakthroughs, suffering from oil production losses and higher operational cost for management of the excessive produced water. A brown field in the south of the Sultanate of Oman was experiencing massive water short circuiting within two of its patterns. [MJO1]While conformance was well established and dynamically confirmed through production performance and artificial lift parameters in most patterns within the field, the complicated inverted nine spot injector-producer pattern scenario[MJO2] was making it difficult to ascertain the offending injectors or unexpected flow paths leading to the condition within the study area. The lower API oil and slightly fractured and faulted geology was exhibiting conditions for injection imbalance and the challenge was to bring the high water-cut wells back to full potential and increase oil output whilst reducing water flow. To investigate the breakthrough occurrences and mitigate the challenge, chemical water tracers were introduced in the reservoir as a part of Integrated Reservoir Management framework to identify flow directions and offending injectors. The Phase-1 of the two-phase study, discussed in this paper, was carried out to determine reservoir conformance that was contributing to short circuiting and once the cause was identified and treated, Phase-2 was carried out post well intervention to validate the success of the treatment. Phase-1 of the tracer study was initiated in October 2019 where two injectors and nineteen producers across two adjacent patterns were traced with two unique chemical water tracers. Massive tracer responses were obtained within the first few days in few wells, directly pointing out towards the offending injector(s). Sampling and analysis for Phase-1 was continued for about six months, after which, a zonal isolation was carried out in one the identified injectors in August 2020. Cement was pumped across all the perforation intervals and a new perforation was performed across the top and bottom of the reservoir avoiding the middle intervals that were taking about 70% of injection as per production logging. Phase-2 of the study was initiated in March 2021 and continued sampling and analyses are still being carried out. With about 15% reduction in water cut and a three-fold increase in oil rate at the target producer, the study validated that an integrated knowledge of reservoir geology and production behavior coupled with tracer studies was a very successful strategy for managing short circuiting in waterflood reservoirs. The study showed that this sequence and combination of methods can be useful in effective treatment for wells experiencing high water cut across the world.

Real-Time EM Look-Ahead Resistivity for Mapping of Oil/Water Contact While Drilling at Low Deviated Well, New Perspective for Mature Oil Fields Development: A Case Study Of Umm Gudair Field, Kuwait

The Umm Gudair (UG) Field is a carbonate reservoir of West Kuwait with more than 57 years of production history. The average water cut of the field reached closed to 60 percent due to a long history of production and regulating drawdown in a different part of the field, consequentially undulating the current oil/water contact (COWC). As a result, there is high uncertainty of the current oil/water contact (COWC) that impacts the drilling strategy in the field. The typical approach used to develop the field in the lower part of carbonate is to drill deviated wells to original oil/water contact (OOWC) to know the saturation profile and later cement back up to above the high-water saturation zone and then perforate with standoff. This method has not shown encouraging results, and a high water cut presence remains. An innovative solution is required with a technology that can give a proactive approach while drilling to indicate approaching current oil/water contact and geo-stop drilling to give optimal standoff between the bit and the detected water contact (COWC). Recent development of electromagnetic (EM) look-ahead resistivity technology was considered and first implemented in the Umm Gudair (UG) Field. It is an electromagnetic-based signal that can detect the resistivity features ahead of the bit while drilling and enables proactive decisions to reduce drilling and geological or reservoir risks related to the well placement challenges.

Production Optimiser Pilot for the Large Artificially-Lifted and Mature Samotlor Oil Field

This paper describes a production optimiser Pilot, developed by Rosneft/Samotlorneftegaz, with support from bp and deployed in JSC Samotlorneftegaz - a vast, mature, water-flooded, high water-cut and artificially-lifted oil field. Objectives include creating a digital twin for a sub-system of 600 wells and ~180 km of pipeline network, applying discrete, continuous and constrained optimisation techniques to maximise production, developing sustainable deployment workflows, implementing optimiser recommendations in the field and tracking incremental value realisation. This proof-of-concept Pilot and field trial approach was adopted to understand the optimisation technology capability and work-flow sustainability, prior to a field-wide roll-out. The periodic optimisation activity workflows include the creation of a "Digital Twin", a validated surface infrastructure model that is fully calibrated to mimic field performance, followed by performing optimisation that includes all the relevant constraints. Optimisation was trialled using two different classes of algorithms – based on sequential-modular and equation-oriented techniques. This strategy minimises optimisation failure risks and highlights potential performance issues for such large-scale systems. Optimiser recommendations were consolidated, field-implemented and values tracked. The optimiser Pilot development was undertaken during the fourth quarter of 2019. The delivered minimum viable product and workflows were used for field trials during 2019-20 and continuously improved based on the learnings. Specialists from both bp and Rosneft, along with three consulting organisations (1 in Russia and 2 in the UK) collaborated and worked as one-team to deliver the Pilot. Optimiser recommendations for maximising production include continuous and discrete decisions such as ESP frequency changes, high water-cut well shut-ins and prioritised ESP lists for installing variable speed drives. Field production increase of 1% was achieved in 2020 and tracked. Enduring capabilities were built, and sustainable work-flows developed. Field-wide optimisation for Samotlorneftegaz is non-trivial due to the sheer size, with over 9,000 active wells and due to continuously transient operations arising from frequent well-work, well shut-in's, new well delivery, pipeline modifications and cyclic mode of operations in some wells. This Pilot has provided assurance for the optimisation technical feasibility and workflow sustainability. A second Pilot of similar complexity but with different pressure-flow system response is planned. The combined results will help to decide about the full-field roll-out for this vast field, which is anticipated to deliver around 1% of additional production. This Pilot has demonstrated the applicability of discrete and continuous variable constrained optimisation techniques to large-scale production networks, with very high well-count. Furthermore, the developed workflows for configuring and calibrating the digital twin have several unique components including automation of hydraulic network model generation from static data, well model build automation and fit-for-purpose automated well model calibration. Overall, the results of this approach demonstrate a viable and sustainable methodology to optimise large-scale oil production systems.