Flow zonation and permeability estimation is a common problem in reservoir characterization; usually, integration of openhole log data with conventional and special core analysis solves the latter. We present a Bayesian based method for identifying hydraulic flow units in uncored wells using the theory of Hydraulic Flow Units (HFU) and subsequently compute permeability using wireline log data.
First, we use the F-test and the Akaike's criteria coupled with a nonlinear optimization scheme based on the probability plot to determine the optimal number of HFU present in the core dataset with the regression match giving the pertinent statistical parameters of each flow unit. Second, we cluster core data into its respective HFU by using the Bayes' rule. Finally, we apply an inversion algorithm based on Bayesian inference to predict permeability using only wireline data.
We illustrate the application of the procedure with a carbonate reservoir having extensive core data. The results showed the Bayesian-based clustering and inversion technique delivered permeability estimates in agreement with core data as well as with results obtained from pressure transient analysis.
Among the applications of the workflow presented are better productivity index assessments, enhanced petrophysical evaluations, and improved reservoir simulation models. Coupling of Nonlinear optimization with Bayesian inference proves a robust way for performing data clustering providing unbiased estimations
Kuwait Oil Company (KOC), one of the most important National Oil Companies (NOC) in the world, is growing in every sense, as the State of Kuwait is seeking to boost its oil production capacity by 2040, in line with the new approved strategy of Kuwait Petroleum Corporation. This growth into the future entails a shift from primary extraction to more complex settings, where new fields are produced simultaneously with others submitted to water flooding, EOR and Steam Injection, in what constitutes one of the biggest challenges ever faced by the company, due to the short timelines involved. The company has a variety of technological partners that include International Oil Companies (IOC), to further support the 2040 strategy of the corporation. This strategic growth vision, not exempted of an increasing breath of challenges, is accompanied by a focused effort in building new technical capabilities in the personnel, and in gradually transforming the way the training plans shape the professional profiles and set the paths for ensuring the specialized skills and expertise that will be needed. This paper describes how KOC is collaborating with an IOC, for uplifting and accelerating the training of its personnel, with the aim of enabling the availability of critical expertise needed to ensure production targets. Selected examples will detail how this cooperation NOC-IOC has been fruitful in enhancing competencies and training workflows. The teams involved from both sides of the spectrum experienced interesting challenges, and did not shy away from applying tactics of management of change to support the evolving talent development ecosystem. An emphasis will be placed in describing why elements like cultural nuances, corporate legacy, communication, alignment and integration are considered key in the implementation of the training strategies. With a well-established KOC competency-based training scheme, and after several years of fruitful exchanges with the IOC, the uplifts achieved in talent development schemes have shaped a transformation journey, with specific results worth sharing.
Richard, Pascal (Shell Global Solutions International BV) | Lamine, Sadok (Shell Global Solutions International BV) | Pattnaik, Chinmaya (Kuwait Oil Company) | Al Ajmi, Neama (Kuwait Oil Company) | Kidambi, Vijay (Kuwait Oil Company) | Narhari, Rao (Kuwait Oil Company) | LeVarlet, Xavier (Shell Kuwait Exploration And Production BV) | Swaby, Peter (Swaby Software Limited) | Dashti, Qasem (Kuwait Oil Company)
The North Kuwait Carbonate (NKJG) reservoirs are currently under development by KOC (Kuwait Oil Company). The appraisal and development of the NKJG offer challenges such as lateral variations in reservoir quality, tight to very tight reservoirs and natural fracturing to a varying degree spatially. The presence of open, connected fractures is one of the key elements to achieve a successful development. Also, the presence of fracture corridors increase the risk associated with drilling. Numerous fracture modelling studies have been supporting both appraisal and development strategies of the fields.
A structural evolution model has been developed based on field observations and linked to the regional phases of deformations. Detailed fracture characterization using static BHI (bore hole images) and core data as well as dynamic data has been achieved. Small scale detailed DFN (Discrete Fracture Network) in support of planning and drilling activities of future appraisal wells has been carried out. Full field DFN in support to production history matching and forecast has been completed. The core and pressure transient analysis data have been used to calibrate the permeability and porosity of the DFN property ahead of the dynamic simulation work.
This paper illustrates some examples of best practices of the various study components with a focus on core to BHI calibration, fracture porosity calibration using core data and calibration of DFN models using pressure transient analysis data.
Lamine, S. (Shell Global Solutions International BV) | Richard, P. (Shell Global Solutions International BV) | Steen, E. Van der (Shell Kuwait Exploration and Production) | Pattnaik, C. (Kuwait Oil Company) | Narhari, R. (Kuwait Oil Company) | LeVarlet, X. (Shell Kuwait Exploration and Production) | Dashti, Qasem (Kuwait Oil Company)
The North Kuwait Carbonate (NKJG) reservoirs are currently under development by KOC (Kuwait Oil Company). In addition to the matrix heterogeneity, natural fracturing poses extra challenges for the optimization of the field development planning. The presence of open, connected fractures presents opportunities for infill drilling but increases the risk of water invasion and drilling related issues. Numerous fracture modelling studies have been supporting both appraisal and development strategies of the fields.
The translation of the field observation and detailed fracture characterization using static BHI (bore hole image) and core data yields a series of geological concepts. These concepts capture end members of the spatial distribution of the major conductive features and provide a range of realizations for the geometrical extent of the fracture zones. Given the large uncertainty in the dynamic properties of the fracture; pressure transient analysis (PTA), complemented by core data, has proven to be key in narrowing the range of fracture equivalent permeabilities and porosities that are carried forward in the history matching step.
This paper focuses on illustrating the integration of different aspects of Pressure Transient Analysis data to pre-condition the discrete fracture network (DFN) model realizations.
Comparison between KH from well test and log data allows to discriminate fractured from matrix wells. Dedicated sector models around fractured wells are built to assess the impact of the matrix, faults and fracture properties on the transient pressure response. Numerical simulations are conducted directly on the static model with the fractures explicitly captured as discrete surface features. For each DFN configuration, a sensitivity analysis of the fracture properties is performed and the characteristics of the resulting pressure derivatives are then compared against the well test data to select the plausible realizations that honor both geological and flow data.
In this paper, a series of examples demonstrating the application of the methodology are presented for different areas of the field.
Jahdhami, Moosa Al (Petroleum Development Oman) | Maag, Jan Willem de (Shell Global Solutions International B. V.) | Mueller, Alexander (Shell Global Solutions International B. V.) | Narhari, Srinivasa Rao (Kuwait Oil Company) | Kolawole, Olusegun (Kuwait Oil Company) | Kidambi, Vijaya Kumar (Kuwait Oil Company) | Al-Qadeeri, Bashar (Kuwait Oil Company) | Dashti, Qasem (Kuwait Oil Company)
Seismic data in Raudhatain field in Kuwait is strongly contaminated with multiples that impair the image of reservoir reflectors and challenge the structural as well as the quantitative interpretation. A reliable reservoir interpretation depends on an optimal attenuation of multiples (free surface and interbed). In this project, we demonstrated that a significant amount of multiple energy was attenuated by implementing 3D SRME together with data and model driven interbed de-multiple using two strong shallow reflectors as the dominant multiple generators.
The project was run with a primary objective of a successful multiple attenuation at the Jurassic level. Initially, 3D Fourier interpolation was applied to regularize and infill shots and receiver independently, to prepare the data for 3D multiple attenuation. However, the survey in some areas was undershot due to agricultural activities, resulting in massive data gaps which presented challenges for data regularization/interpolation.
Since the 3D data interpolation results demonstrated that this approach was suboptimal and inadequate to infill all data gaps, especially the large ones, a new strategy of incorporating legacy data (from the same area), was followed to infill these gaps in a more appropriate way.
The 3D merged dataset (vintage and new data) was used as input for 5D interpolation software which regularizes and infills the data in 5D senses producing fully regular Common Offset Vector (COV). The 5D interpolated COV panels show a significant improvement to the 3D interpolation results. With the incorporation of vintage data and implementation of 5D interpolation, the multiple predictions were improved.
After applying 3D SREM on the data, 3D interbed demultiple was implemented assuming that the dominant multiple periodicity at the target level is related to two shallow reflectors which have approximately 138ms TWT separation. As the real shallow data was too poor to use, full waveform inversion velocities were used to model the reflectivity of the shallow overburden, which used as input for 3D interbed multiples prediction together with the actual data. This 3D data and model driven approach successfully predicted the 1st order interbed multiples bouncing between these two reflectors.
This advanced 3D de-multiple approach has significantly attenuated multiples at target level allowing more reliable interpretation of the reservoir sections. Robust data interpolation and optimal implementation of novel multiple attenuation techniques were the key elements to the success of this project. Following the same processing approach on surveys or data with similar issues and challenges will help to address the seismic multiples and improve the reliability and accuracy of reservoir interpretation.
Al Jahdhami, Moosa (Shell Global Solutions International B.V.) | de Maag, Jan (Shell Global Solutions International B.V.) | Mueller, Alexander (Shell Global Solutions International B.V.) | Narhari, Srinivasa (Kuwait Oil Company) | Kolawole, Osuntola Olugesun (Kuwait Oil Company) | Kidambi, Vijaya (Kuwait Oil Company) | Al-Qadeeri, Bashar (Kuwait Oil Company) | Dashti, Qasem (Kuwait Oil Company)
Summary Seismic data in Raudhatain field in Kuwait is strongly contaminated with multiple energy that impairs the image of reservoir reflectors, and challenges the structural as well as the quantitative interpretation of the reservoir. A reliable reservoir intepretation depends on an optimal attenuation of multiple energy (free surface and interbed). In this project we demonstrated that a sigificant amount of multiple energy was attenuated by implementing 3D SRME along with data and model driven interbed de-multiple that uses two strong shallow reflectors as the dominant multiple generators. Introduction Kuwait Oil Company (KOC) in 2011 acquired large scale single sensor accelerometer data covering most part of North Kuwait fields. Processing of 180 km2 of this single sensor data was awarded to Shell with a scope of multiple attenuation by implementing advanced de-multiple techniques.
Bharti, Satyam (Shell Global Solutions International) | Stopin, Alexandre (Shell Global Solutions International) | Solano, Carlos Andres Perez (Shell Global Solutions International) | Plessix, Rene-Edouard (Shell Global Solutions International) | Lutz, Jos (Shell Global Solutions International) | Al-Qadeeri, Bashar (Kuwait Oil Company) | Dashti, Qasem (Kuwait Oil Company) | Narhari, Srinivasa (Kuwait Oil Company) | Kolawole, Osuntola Olugesun (Kuwait Oil Company)
To retrieve an accurate velocity profile of about the first kilometer depth of a field in North Kuwait, we apply a 3-D vertical transverse isotropic elastic multi-parameter waveform inversion to a low-frequency, wide-aperture land data set. Although we focus the inversion on the diving compressional waves, accounting for the elastic energy conversion around the large velocity contrasts helps to stabilize the inversion. During the inversion we kept the shear-to-compressional velocity ratio unchanged and inverted for the NMO velocity and the η-parameter. We carried out the inversion up to 6 Hz. The multi-parameter elastic waveform inversion notably helps to better focalize the tops of the Dammam and Rus formations.
Presentation Date: Tuesday, October 18, 2016
Start Time: 3:20:00 PM
Presentation Type: ORAL
The productivity of wells drilled into naturally fractured reservoirs is often unpredictable due to the highly heterogeneous nature of the reservoir. In such reservoirs, productivity is a function of complex processes involving the density and aperture of fractures, their interconnectivity and the quality of the surrounding rock matrix. For reducing the risks associated with drilling of new wells for field development, one approach consists in creating multiple equiprobable reservoir models constrained to both static and dynamic data. We further propose to associate with each of these models a synthetic indicator, represented by a single scalar 3D property accounting for modelled fracture properties and correlated with the expected productivity of future wells. This workflow was applied to a group of fractured carbonate reservoirs in Kuwait which helped in designing new horizontal wells.
The developed methodology focuses on capturing accurately the lateral and vertical heterogeneity of the fracture network. Image log data analysis shows that the vertical changes of fracture density are dominated by facies variations, whereas areal contrasts are primarily related to the location of the main faults and folds. In some of the modeled scenarios, the orientation of secondary fractures, developed during the latest tectonic phases, is assessed using paleo-stress modeling. Fracture length parameters are inferred from the comparison between percolating volumes extracted from detailed connectivity analysis of discrete fracture networks and qualitative well test interpretations. Fracture aperture and permeability are finally calibrated against production history in small scale sector models. Once the initial sectors have been prepared by a reservoir engineer, this "big-loop" calibration process, which involves modifying the geological fracture model, upscaling it and running the flow simulation, is performed directly by the geologist, ensuring the consistency of the final simulation model. For better understanding the impact of matrix properties and fracture porosity, permeability and shape factor on well productivity, thousands of simulations are run on a small-scale synthetic model, yielding a multi-dimensional lookup table giving the potential productivity as a function of the fracture network characteristics.
Six different scenarios involving changes of fracture densities, orientations and aperture are explored. These scenarios are consistent with fractures interpreted on image log data, with the major structural elements and with historical production data. Using the big-loop calibration, most of the history matching work is performed in the static model. The planning of new wells was then achieved by targeting zones which have been identified as highly productive in all the modeled scenarios.
Innovative techniques are used for decoupling the vertical and lateral heterogeneity modeling for deducing fracture length from percolation analysis and for performing aperture calibration to production data. The methodology we propose for computing a productivity indicator enables rapid assessment of the flowing potential of fractured reservoirs.
This architecture is a result of a study completed for the Kuwait Oil Company under the Enhanced Technical Services Agreement with Shell. Specifically this covered subsurface data management. Several visits to Kuwait were required and during interviews with key stakeholders gaps where identified and many issues highlighted. The recommended architecture was modified to incorporate these requirements and finally agreed and approved.
This architecture was centered on having a QCed data store with seamless integration to KOC current existing systems. This reduced cost by the elimination of the need to introduce a new database. Further, this structure built on the existing knowledge base in place was a key factor in the architecture approval.
The existing fragmented systems were characterized by different data values and data in several locations. There was a clear need for an integrated QCed data store. The need for clear accountabilities and for different disciplines to work together more closely was very much evident. The concept is derived from our Shell architecture structure concept but utilizing KOC existing systems. The focus in this architecture is on the seamless integration and defining clear data flows and roles and accountabilities.
Each data type is covered by flow charts to specify the flow of data and the assigned focal points responsibilities and how the data is managed throughout the process.
The structure and process is intended to keep the master data store always current with the latest QCed data. Uploading and quality review of the initial data set is therefore a key first step.
With clear accountabilities and responsibilities defined and a clear data workflow the data store will be always in good shape. Having the QCed assured data at your fingertips saves a lot of time and money.
Having the technical user in ownership of his data and resposible on it's evergreening will assure the rest of the technical community they are using the latest most QCed data.
Fava, Guido (Schlumberger) | Descubes, Elena (Schlumberger) | Daoud, Ahmed (Schlumberger) | Sharifzadeh-Najafi, Ahmad (Schlumberger) | Al-Enezi, Bashayer (Kuwait Oil Company) | Al-Arouj, Mutlaq (Kuwait Oil Company) | Dashti, Qasem (Kuwait Oil Company)
Sabriyah and Raudhatain are the main fields producing from the Middle Marrat Jurassic formation in North Kuwait with approximately 5 km distance between the two fields. Raudhatain fluid is considered as Volatile Oil, while Sabriyah is described as Gas-condensate. 16 PVT samples from Raudhatain were analyzed and described as Volatile oil. 12 PVT samples taken from Sabriyah field where 7 samples show gas condensate behavior and rest shows volatile oil.
A key challenge in understanding the Sabriyah fluid characterization is the fact that 5 well samples that showed Volatile oil behavior are not separated from the Gas condensate wells by any apparent barrier. In addition, the initial reservoir pressure is much higher than the saturation pressure, preventing the equilibrium of those fluids.
The objectives for this study are to analyze the physical explanation of coexistent of oil and gas-Condensate in one communicated reservoir with reservoir pressure higher than saturation pressure, apply different modeling approaches to accurately describe the fluid behavior in Sabriyah field and finally capture the influence of uncertainty in the type of fluid on the production forecast.
The physical explanation for this phenomenon was investigated from different points of view: the variation of temperature, compositional variation with depth, existence of geological barriers, and facies changes. It was found that the compositional variation with depth and the change of fluids with changes of facies can provide reasonable explanation for this phenomenon. The first explanation related to compositional variations with depth is supported by the observed data that shows a strong relationship between depth and fluid type, while the temperature did not influence significantly the gas-oil phase change. The second explanation related to the concept of gas and oil charge depending on facies is supported by mercury injection capillary pressure data taken from different depth in the reservoirs, this concept improves the understanding of fluid distribution which could not be explained in previous approaches.
This paper shows the way of modeling this phenomena based on these two explanations, which honor both static and dynamic data with special reference to the effect of these different modeling approaches on the production forecast of Sabriyah field.
The near critical fluids which are the type of fluids in Sabriyah field are usually problematic to handle with Equation of State; therefore solving this particular case is expected to add technical value to reservoirs of the same type of fluids.
The facies dependence of gas and oil distribution and the way of modeling this phenomenon is an innovative view that can contribute to the description of similar fields.