Reliability of subsurface assessment for different field development scenarios depends on how effective the uncertainty in production forecast is quantified. Currently there is a body of work in the literature on different methods to quantify the uncertainty in production forecast. The objective of this paper is to revisit and compare these probabilistic uncertainty quantification techniques through their applications to assisted history matching of a deep-water offshore waterflood field. The paper will address the benefits, limitations, and the best criteria for applicability of each technique.
Three probabilistic history matching techniques commonly practiced in the industry are discussed. These are Design-of-Experiment (DoE) with rejection sampling from proxy, Ensemble Smoother (ES) and Genetic Algorithm (GA). The model used for this study is an offshore waterflood field in Gulf-of-Mexico. Posterior distributions of global subsurface uncertainties (e.g. regional pore volume and oil-water contact) were estimated using each technique conditioned to the injection and production data.
The three probabilistic history matching techniques were applied to a deep-water field with 13 years of production history. The first 8 years of production data was used for the history matching and estimate of the posterior distribution of uncertainty in geologic parameters. While the convergence behavior and shape of the posterior distributions were different, consistent posterior means were obtained from Bayesian workflows such as DoE or ES. In contrast, the application of GA showed differences in posterior distribution of geological uncertainty parameters, especially those that had small sensitivity to the production data. We then conducted production forecast by including infill wells and evaluated the production performance using sample means of posterior geologic uncertainty parameters. The robustness of the solution was examined by performing history matching multiple times using different initial sample points (e.g. random seed). This confirmed that heuristic optimization techniques such as GA were unstable since parameter setup for the optimizer had a large impact on uncertainty characterization and production performance.
This study shows the guideline to obtain the stable solution from the history matching techniques used for different conditions such as number of simulation model realizations and uncertainty parameters, and number of datapoints (e.g. maturity of the reservoir development). These guidelines will greatly help the decision-making process in selection of best development options.
Along-hole depth is the most fundamental subsurface measurement made in our business. Driller's depth, the basis of logging while drilling (LWD) data registration, and wireline logged depth are the primary sources of along-hole depth data. These are rarely congruent. This paper sets out a methodology that can be applied to both wireline and drill pipe along-hole depth measurement (Driller's Way-point Depth, DwpD) and provides an uncertainty calculation that results in True Along-hole (TAH) depth. The result is a reduction in differences between drill pipe and wireline depth measurements, increasing confidence in along-hole depth measurements and increasing well data value. A field data set is reviewed that showed up the similarities and the differences between DwpD and the wireline corrections.
Maleki, Masoud (Uuniversity of Campinas UNICAMP) | Danaei, Shahram (Uuniversity of Campinas UNICAMP) | Davolio, Alessandra (Uuniversity of Campinas UNICAMP) | José Schiozer, Denis (Uuniversity of Campinas UNICAMP)
Permanent Reservoir Monitoring (PRM) in systems deep-water settings provide on-demand snapshots for hydrocarbon reservoirs at different times during their production history. Delays in the interpretation turnaround of 4D seismic data reduce some benefits of the PRM. These delays could adversely impact the decision making processes despite obtaining information on demand. Using fast-track approaches in 4D seismic interpretation can provide timely information for reservoir management. This work focuses on a fast-track 4D seismic qualitative interpretation in PRM environment, with the aim of choosing the best seismic amplitude attribute (4D) to use. Different seismic attributes are extracted and the one with high signal-to-noise ratio is selected to carry out the 4D qualitative interpretation. All 4D signals are juxtaposed with well production history data to increase confidence in our interpretation. The selected attribute can be interpreted and used for the foreseeable life of field. This workflow has been developed and applied on post-salt Brazilian offshore field to choose the best seismic attribute to conduct the 4D seismic qualitative interpretation.
Simões Maciel, Rodrigo (Federal University of Espírito Santo) | Ressel Pereira, Fábio de Assis (Federal University of Espírito Santo) | Fieni Fejoli, Rômulo (Federal University of Espírito Santo) | Leibsohn Martins, André (Petrobras) | Duarte Ferreira, Marcus Vinicius (Petrobras)
Petrobras has faced several challenges concerning inorganic scaling in the Pre-salt cluster. Scale prediction plays an important role on well completion selection and supporting to define better alternatives for chemical injection location. However, predicting scale in wellbores is traditionally performed based on thermodynamical equilibrium of the formation water under static conditions. This strategy leads to conservative results since it neglects hydrodynamics and kinetics of the scaling process. This paper proposes a new approach to predict scaling in downhole conditions. The study seeks to contribute on the comprehension of the effect of fluid flow and equipment geometry variation in the crystal deposition process in intelligent well completion equipment.
Such completion devices act in managing the fluid flow influx from different reservoirs or multiple zones of the same reservoir. Despite the positive aspects of this technology, some authors have been pointing out some problems associated with specific applications of these tools. The most common issues are related to the considerable pressure differential and the occurrence of calcium carbonate (CaCO3) scale. The pressure drop in this tool induces the flash liberation of CO2 from the aqueous solution. Consequently, the chemical equilibrium is displaced towards the direction of precipitation of CaCO3 in the flow stream. This paper proposes a new approach to predict scaling in downhole conditions and aims to quantitatively evaluate the calcium carbonate precipitation on the smart completion element internal surfaces. Computational Fluid Dynamics (CFD) along with discrete phase modeling (DPM) is employed to simulate the transport and adhesion of the calcium carbonate crystals on the device. The valves geometries consider the main features observed on the field according to different suppliers, accounting the different possibilities of completion geometries for Brazilian Pre-Salt environment.
The results showed the tendency of scale deposition pointing out hot spots in several different completion accessories at downhole conditions. A better understanding of the scale potential has influenced the decision-making process on the completion design and workover alternatives in the Pre-salt wellbores.
The formation and deposition of solids including mineral scale, paraffin, and asphaltene, may occur at any location of the oil and gas production system, from the bottom of the well to a gathering facility, due to the changes in the physical and chemical conditions associated with production fluids. Depositions can reduce the formation permeability, reservoir transmissibility and have detrimental impact on production rates during oil and gas production. Common practice is to complete the well and then apply a treatment and remediation program as necessary, including squeeze treatments and batch treatments.
Horizontal, multi-stage hydraulic fracturing is widely used in the industry as stimulation practice.
This paper reports on a new, slow-release particle technology developed for applications in hydraulic fracturing. This new technology does not rely on adsorption, impregnation or any other technology of embedment of additives onto a substrate. The new slow-release particles exhibit improved delayed release profile, high strength, and the capacity to incorporate active components, such as scale or paraffin inhibitor, either singly or in combination.
Hjeij, Dawood (Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University) | Abushaikha, Ahmad (Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University)
Most commercially available simulators use the trivial two-point flux approximation (TPFA) method for flux computation. However, the TPFA only gives consistent solutions when used for K-orthogonal grids. In general, multi-point flux approximation (MPFA) methods perform better under both heterogeneous and anisotropic conditions. The mimetic finite difference (MFD) method is designed to preserve properties on unstructured polyhedral grids, and its development for simulating full tensor permeabilities is also crucial step. This paper compares the performance, accuracy, and efficiency of these schemes for simulating complex synthetic and realistic hydrocarbon reservoirs.
Taha, Taha (Emerson Automation Solutions) | Ward, Paul (Emerson Automation Solutions) | Peacock, Gavin (Emerson Automation Solutions) | Heritage, John (Emerson Automation Solutions) | Bordas, Rafel (Emerson Automation Solutions) | Aslam, Usman (Emerson Automation Solutions) | Walsh, Steve (Emerson Automation Solutions) | Hammersley, Richard (Emerson Automation Solutions) | Gringarten, Emmanuel (Emerson Automation Solutions)
This paper presents a case study in 4D seismic history matching using an automated, ensemble-based workflow that tightly integrates the static and dynamic domains. Subsurface uncertainties, captured at every stage of the interpretative and modelling process, are used as inputs within a repeatable workflow. By adjusting these inputs, an ensemble of models is created, and their likelihoods constrained by observations within an iterative loop. The result is multiple realizations of calibrated models that are consistent with the underlying geology, the observed production data, the seismic signature of the reservoir and its fluids. It is effectively a digital twin of the reservoir with an improved predictive ability that provides a realistic assessment of uncertainty associated with production forecasts.
The example used in this study is a synthetic 3D model mimicking a real North Sea field. Data assimilation is conducted using an Ensemble Smoother with multiple data assimilations (ES-MDA). This paper has a significant focus on seismic data, with the corresponding result vector generated via a petro-elastic model. 4D seismic data proves to be a key additional source of measurement data with a unique volumetric distribution creating a coherent predictive model. This allows recovery of the underlying geological features and more accurately models the uncertainty in predicted production than was possible by matching production data alone.
A significant advantage of this approach is the ability to utilize simultaneously multiple types of measurement data including production, RFT, PLT and 4D seismic. Newly acquired observations can be rapidly accommodated which is often critical as the value of most interventions is reduced by delay.
A challenging problem of automated history-matching work flows is ensuring that, after applying updates to previous models, the resulting history-matched models remain consistent geologically. To enhance the applicability of localization to various history-matching problems, the authors adopt an adaptive localization scheme that exploits the correlations between model variables and observations. This paper presents a novel approach to generate approximate conditional realizations using the distributed Gauss-Newton (DGN) method together with a multiple local Gaussian approximation technique. This work presents a systematic and rigorous approach of reservoir decomposition combined with the ensemble Kalman smoother to overcome the complexity and computational burden associated with history matching field-scale reservoirs in the Middle East. This paper presents a comparison of existing work flows and introduces a practically driven approach, referred to as “drill and learn,” using elements and concepts from existing work flows to quantify the value of learning (VOL).
In need of an exploration boost, Norway doled out a record 83 production licenses in mature areas of the Norwegian Continental Shelf to 33 firms. Norway hopes for a continued rise in offshore exploration and development activity to ensure steady oil and gas production through the next decade. Equinor has grabbed seven new licenses in the Barents and Norwegian Seas, the latest in a flurry of offshore activity in which the firm has added acreage off the UK and Brazil, gained approval for a big Arctic project, and awarded billions of dollars in service contracts. A reservoir-conditions coreflood study was undertaken to assist with design of drilling and completion fluids for a Norwegian field. Multiple fluids were tested, and the lowest permeability alterations did not correlate with the lowest drilling-fluid-filtrate-loss volumes.
Africa (Sub-Sahara) Aminex Petroleum Egypt (APE), a subsidiary of UK-based Aminex, discovered oil at its South Malak-2 (SM2) well on the West Esh el Mellaha-2 concession in Egypt. Tests showed flow rates of approximately 430 B/D of 40 API gravity crude oil. Based on the findings at SM2, a full field development program will be presented to the Egyptian authorities and the joint venture partners before commercial development. APE is the operator of the license with partner Groundstar Resources. Foxtrot International discovered oil and gas at its Marlin North-1 well in Block CI-27, offshore Cote d'Ivoire. A 22-m perforated section of a gas-bearing column in a Turonian interval flowed at a stabilized rate of 25 MMcf/D of gas and 150 B/D of condensate through a 46/64-in.