Kuwait Oil Company

Presence of H₂S detected in producing wells of North Kuwait sweet waterflooded reservoirs over the last 18 years, gave indications of biogenic souring. In response to this, the Kuwait Oil Company engaged in detailed souring potential assessments of selected reservoirs such as the Raudhatain Mauddud (RAMA), to predict the further generation of H₂S and define the required souring mitigation strategy to ensure safe production over the remaining field life.

The souring simulation modelling was conducted on the RAMA subsurface model with support from Shell, using a state of the art souring prediction program. The initial phase of the study consisted in the history match simulation to define the most likely souring mechanism in the field. The forecast considered various scenarios with a range of sensitivities on carbon nutrient and sulphate levels, both in formation and injected water in the field.

The history match simulation results showed a good correlation with most of the producers with available H₂S data. The Forecast simulation over the next 15-year period predicts a moderate souring severity for this reservoir, based on the maximum H₂S mass flow rate of 90 kg/d and H₂S in gas maximum concentration of 85 ppmv at the field level.

This work provides the petroleum Industry further insights into the souring behavior when effluent water is injected in addition to seawater, particularly the effects of additional carbon nutrients fed into the reservoir.

Management of oil and gas resources and reserves has always been complex process as the company’s portfolio consists of resource and reserves volumes with varying degrees of uncertainty and maturity levels of projects. Some of the hydrocarbon volumes are from resources that are highly uncertain and require technology imprevoments or breakthroughs. However, for strategy formulation of the country/company needs consideration of all hydrocarbon volumes that can generate value in the future. The prioritization of development strategies for its reservoirs based on rigorous technical and economic assessments while protecting the national interests is a challenging task.

Kuwait Oil Company (KOC) has been using multiple systems for both asset and business planning processes that is not optimized for faster turnaround. The proposed integrated and automated reserves management solution provided a structured environment for systematic economic evaluation and portfolio optimization. It facilitates the visualization of key reservoir parameters delivering full understanding of the forecasted reserves, production and economic potential of the entire company. It indentifies gaps between reserves and detailed development plans based on technical and commercial criteria. By Optimizing the project timing and economics results in reduction of budgetary expences, increase in portfolio revenue and greater confidence for the company. Ranking the investment opportunities helps in allocating resources appropriately amongst different projects in a systemic manner to ensure profitability of the company. This approach provides ease to KOC in modeling complex scenarios and quickly evaluate a wide range of different development strategies catering for risk and uncertainty

This paper describes current industry challenges in resource and reservoir management, and an integrated approach to reserves, economics and portfolio management envisioned for Kuwait Oil Company (KOC) which will assist in identifying optimal reservoir development options to meet any defined strategic goals. The results and benefits gained after deployment of pilot will also be explained in the paper. This integrated approach for optimization of Asset Action Plans is a unique solution and would prove beneficial for our industry.

Burgan Marrat, a deep carbonate reservoir was transferred from exploration to development team for an accelerated production of the newly discovered oil. This multi-billion barrel reservoir is spread over 450 km², has more than 40 faults, 8 compartments with large variation in oil-water contact and reservoir/fluid characteristics. The objective of this work is to understand the key uncertainties and quantify their impact on the reservoir offtake rate and oil recovery by conducting uncertainty assessment.

An interdisciplinary team identified the key uncertainty parameters expected to have significant impact on the reservoir development. The range and probability distribution law for each parameter was set considering the uncertainties due to limited measurements or variation in interpretations. A Response Surface Model (RSM) was created to evaluate the uncertainties by using a base dynamic model and applying an appropriate experimental design, which allowed to efficiently study the uncertainty space with a feasible number of simulations. Using the RSM, the primary effects and interaction between parameters were quantified to rank the uncertainties based on their impact on field production.

Key uncertainty parameters were identified including eight OWCs, six fault transmissibilities, horizontal and vertical permeability multipliers, and porosity multiplier. Latin Hypercube was found to be the appropriate Experimental Design for the study considering 17 parameters and the need of building a reliable RSM that includes interactions between them. The design recommended 155 simulation cases, which were prepared and submitted automatically by the software.

Multi-time Responses were analyzed qualitatively to identify the top 5 uncertainties having material impact on field production over 20 years considering 6 existing wells and 30 new well locations. The RSM quantitative evaluation showed three parameters (OWC2, OWC4 and OWC1) having a total effect on the response higher than 10%; followed by PERMX and OWC3 with less than 5%. The other 12 parameters have total effects less than 2%, and the interactions effect is less than 0.5% for any interaction between two parameters. Contrary to the intuition, none of the faults proved impact on the reservoir production.

The results prove very useful to make a right development and appraisal strategy in early life of the reservoir. The new well locations can be ranked and prioritized to optimize the development and effectively appraise the areas with high risks.

Uncertainty assessment has value throughout the life of the reservoir. However, this study indicates that its application in early life of the reservoir can bring immense value. An uncertainty analysis on the reservoir production helps in decision-making regarding the number of wells and their locations to reach a target production by managing the risks.

Project deliverables included gravel foundation preparation, concrete foundation installation, equipment reception and installation of conventional beam pumping units at 660 production wells in a remote field in Kuwait with a deadline of six months from equipment arrival. Equipment shipments schedules were sequential and therefore an execution strategy was required to successfully meet the project deadline. This paper describes the field operations strategy devised and adopted to successfully meet the deadline. A temporary operations base was set up at the remote field for coordination, equipment reception, inspection, consolidation, pre-assembly and dispatches. Operations were divided into six parallel processes as follows: 1. Equipment logistics 2. Gravel foundation preparations 3. Concrete foundation installations 4. Unit Pre-assembly 5. Pre-assembled units dispatches 6. Final unit installations Daily output targets were set for each process prior to the commencement of operations.

This paper presents a case history application of real-time fiber-optic technology in the Bahrah oil field, onshore Kuwait. A primary challenge during openhole swellable packer completion operations with multistage fracturing is understanding the number of fractures induced in the formation, particularly in heterogeneous formations where the fracture pressure energy will be distributed along the openhole section. Therefore, fiber-optic technology was selected for the Bahrah project. The application consists in diagnosing a tight carbonate reservoir after multistage acid fracturing and milling the baffles of a production sleeve completion to obtain a well production profile. This technology consists of a fiber-optic cable and a modular sensing bottomhole assembly (BHA). The fiber-optic cable provides distributed temperature sensing (DTS), whereas the BHA is used to monitor pressure, temperature, and the casing collar locator (CCL) in real time.

The usual procedure when using conventional coiled tubing (CT) to stimulate a carbonate openhole section is to treat all pay zones with acid and diverter, which increases both operation time and operational costs. In addition, inadequate control of the treatment placement will often result in ineffective stimulation. When using the fiber-optic technology, monitoring is performed by analyzing the distributed temperature profiles both before and after stimulation; the BHA helps ensure that the optimum pressure is maintained and that the fluid is placed accurately through depth correlation sensors. All components of this intervention are performed in a single trip, which reduces both costs and operation time.

This paper presents an application that uses the modular sensing BHA to improve the performance of milling balls and baffles in the horizontal production sleeve completion. Afterward, DTS is used to diagnose the reservoir performance after multistage acid fracturing to identify fracture initiation points (FIPs). This assists in design optimization, provides better understanding of formation properties, and helps determine the flow rate distribution of each stage across the entire lateral. Another application uses DTS to obtain the production profile of a 3,286-ft horizontal section while flowing back the well through an electrical submersible pump (ESP). The paper presents the methodology and results of these applications.

Using this technology in the petroleum industry helps reduce operation time by up to 50% as a result of performing various CT activities in a single run. This eliminates the need for additional logging or slickline runs using the same BHA, after performing the milling operation to collect DTS data for FIPs and flow rate distribution analysis in the same run. It also reduces costs by enabling real-time decision-making capabilities and effective stimulation.

Waterflood (WF) is the main drive mechanism of North Kuwait reservoirs. Different development strategies has been adopted to develop a giant carbonate reservoir in the asset. Irregular scheme of WF has been implemented in the last 5 years which made it challenging to properly evaluate the WF performance. This paper presents both numerical and analytical approaches to assess the current performance of the waterflood in this reservoir.

The first method uses actual production and injection data to generate traditional waterflood plots such WOR vs. Np, injection throughput, VRR and other diagnostics.

The second approach uses the numerical model to understand the fluid movements in terms of production and water injection. A high resolution model is used to know about the horizontal producers and injectors WF scheme. Streamline model tool is used to understand how the injectors impact their surrounding producers. Injector's efficiency, allocation factors and reservoir sweep efficiency are calculated using the simulation model.

Both approaches are compared to have a better evaluation of the waterflood.

When the waterflood started, a regular i-9 spot patterns was the way to develop the reservoir. The heterogeneity of the reservoir was observed clearly in the different performance of each pattern. Also, high permeability layer (thief zone) has adversely affected the reservoir performance during WF.

The sharp increase of water cut with very low corresponding recovery factor triggered a paradigm shift in developing this waterflooded reservoir. Injecting in lower layers and producing in upper layers (horizontal wells) was the next stage. This brought a great challenge to assess the performance of this WF scheme. Evaluating such a development strategy remains a achallenge.

Subsurface petroleum industry is burdened with uncertainties in every aspect from exploration to production due to limitations of accessibility to reservoir and technology. The most important tools used to understand, quantify and mitigate the uncertainties are geostatistical static modeling and numerical dynamic simulation geomodels. Geomodels are widely used in the industry for characterizing the reservoir and planning favorable development strategy. It is vital instrument for maximizing asset value and optimize project economics.

Static geomodels are foundation for all the advanced numerical and analytical solutions to solve the intricacies of reservoir performance. At the same time, it is where all the static and dynamic geological and engineering observations get integrated to develop common understanding of the reservoir for future studies. Understanding of the above observations and imaging of reservoir framework by individual is the basis for building static geomodels. Hence, at time, the process is highly subjective and proper QC'ing of the models to achieve the general and specific modeling objectives becomes imperative. Simple Questionaries’ based QC'ing and ranking methodologies are also controlled by subjectivity and individual preferences.

In the present endeavor, quantitative ‘Key Performance Indicators (KPIs)’ based standard static geomodeling practices and QC'ing methodologies at corporate level are developed in specially designed "Process Implementation Project (PIP) – Hydrocarbon resource and Uncertainty Management"’ under the aegis of ‘Kuwait Oil Company (KOC) - Reservoir Management Best Practices Steering Committee'.

The main objectives are to establish a practical modeling process, workflows and criteria to standardize modeling processes. A structured self-guidling modeling document has been developed with self-assemment guidelines and questionary. Finally, for each individual process a set of KPIs are specified as minimum standard to meet to obtain the approval of static model.

The present efforts are important for any geologists, geomodelers and reservoir engineers dealing with geostatistical and numerical reservoir modeling and will provide the KPI's based general practices for quality assurance (QA) and QC'ing of the models.

KOC has been producing oil using dual completions from different pressure regime zones from the same well and South East Kuwait field has many such dual completions wells which are currently being converted from natural flow completion to artificial lift completions. In one of such dual completion naturally producing well, first time in world an artificial lift system - Anchor Pump was installed in Short String (SS) through rigless intervention. Thus project well had un conventional dual completion in the field first of its kind i.e. Sucker Rod Pump (SRP) installed in short string and natural producer through Long String(LS). The well produced for some time through both strings and an intervention by workover rig was required due to high water cut and stuck anchor pump in short string. The paper describes the challenges and initiatives and learnings for safe execution of unconventional dual completion well workover.

Due to combination of natural flow and SRP artificial lift completion, the X-mas tree configuration and associated surface equipment of such well was had several constraints and HSE issues for mobilization of rig and dual production zones with varying pressure regimes have challenges of initial well killing due to plugged short string by stuck anchor pump. The risks were identified during planning stage and risk reduction measures were jointly agreed with Field Development. Various options were explored to minimize risks to ALARP level and subsequently addressed in Work Over Program. The surface equipment constraints were eliminated through rigless works and X-tree configuration were modified to suit deployment of a workover rig. Well process safety principles were applied to accomplish initial well killing in both production zones so as to safely pull out existing dual string completion without any well control issues. An initiative to use sucker rod back off tool, first time and safe back off operation was performed successfully from very close to stuck point.

The existing completion strings were pulled out and further well cleanout and workover program was well cleanout Finally, well was completed with new ESP completion string and successfully production tested. The most important factor in success was proactive planning keeping in view of Process Safety for well control issues and effective communication among the concerned parties.

The initiatives adopted in execution of such a challenging well intervention resulted enhancement in safety to rig crew and Rig operational safety standards in addition to contribution towards cost reduction. Lessons learnt has potential of rig time saving specially during workover of large number of heavy oil wells where stuck sucker rod conditions are very common due to sand invasion in tubing during production.

This paper describes the mobilization of a snubbing unit and blowout preventer (BOP) stack in the Middle East and their use to enable the control of a well with an underground blowout and surface broaching within a short time. The mobilization timeline is provided, along with details about how the snubbing unit and BOPs were integrated with existing equipment to enable re-entry into the blowout well. The procedures and equipment used to enable a stable rig up and well entry are discussed. The paper also describes the situation within the well and the procedures used to enable control. Changes to the original plan, the reasons for the changes, and the results are also described.

Mobilization, rig up, and testing were completed within 12 days of receiving instructions to proceed. The well was controlled and left in a safe condition within an additional 14 days. The original plan had to be continuously reviewed and modified as more information became available during the snubbing operation. The original plan was to slip and shear the holed completion out of the well under pressure; however, as described in the paper, this plan was not implemented. The rapid deployment and use of the snubbing unit brought control to a deteriorating situation. Snubbing provided the fastest option to gain control of this well with an underground blowout and surface broaching.

A few horizontal wells were drilled in Kuwait, heavy oil field, as a part of cold production testing. Various workover interventions were performed on these wells. However, some of the wells showed sharp production decline and were producing below expectations. It was suspected that formation damage may have occurred in these ultra-low reservoir pressure wellbores due to the overbalance of the fluids used during interventions.

Concentric coiled tubing (CCT) technology comprising of a downhole jet pump, was recently employed for the first time in Kuwait and was determined to be an effective method to clean the horizontal sections and investigate the reasons for the production problems. The single phase cleanout fluid is circulated down the inner string to power the jet pump, creating a localized drawdown that vacuums the formation solids or fluids out of the wellbore and the combined sand/fluid stream returns via the CCT annulus. The multiple operating modes provided the benefit of cleaning and treating the wellbore in the same run.

This specialized system was successfully utilized to remove sand, evaluate the formation damage and enhance production; meeting all objectives in a single well intervention. Pressure and temperature gauges run below the tool on two wells recorded bottomhole pressure of only 150 psi. Post-production results has pushed the boundaries of the well interventions in heavy oil field in Kuwait and has unlocked several wellbore cleanout and formation damage evaluation opportunities using the CCT technology.

This paper reviews the benefits of the concentric coiled tubing technology and provides a comprehensive case study of the first three horizontal wells. The analysis of the sand and fluid influx profiles obtained during the vacuuming process assisted in to evaluating well production provided crucial data in formulating a management strategy.