In this paper we present our results, challenges and learnings, over a two-year period wherein robust multiobjective optimization was applied at the Mariner asset which is being currently developed. Many different problems were solved with different objectives. These problems were formulated based on the phases of planning and development at the asset. The optimization problems include drilling order and well trajectory optimization as the main objectives with reduction in water cut and reduction of gas production to minimize flaring as secondary objectives. We use the efficient stochastic gradient technique, StoSAG, to achieve optimization incorporating geological and petrophysical uncertainty. For some problems computational limitations introduced challenges while for other problems operational constraints introduced challenges for the optimization. Depending on the problems significant increases between 5% and 20% in the expected value of the objective function were achieved. For the multi-objective optimization cases we show that nontrivial optimal strategies are obtained which significantly reduce (40% decrease) gas production with minimal loss (less than 1%) in the economic objective. Our results illustrate the importance of flexible optimizations workflows to achieve results of significant practical value at different stages of the planning and development cycle at an operational asset.
The in-situ steam based technology is still the main exploitation method for bitumen and heavy oil resources all over the world. But most of the steam-based processes (e.g., cyclic steam stimulation, steam drive and steam assisted gravity drainage) in heavy oilfields have entered into anexhaustion stage. Considering the long-lasting steam-rock interaction, how to further enhance the heavy oil recovery in the post-steam injection era is currently challenging the EOR (enhanced oil recovery) techniques. In this paper, we present a comprehensive review of the EOR processes in the post steam injection era both in experimental and field cases. Specifically, the paper presents an overview on the recovery mechanisms and field performance of thermal EOR processes by reservoir lithology (sandstone and carbonate formations) and offshore versus onshore oilfields. Typical processes include thein-situ combustion process, the thermal/-solvent process, the thermal-NCG (non-condensable gas, e.g., N2, flue gas and air) process, and the thermal-chemical (e.g., polymer, surfactant, gel and foam) process. Some new in-situ upgrading processes are also involved in this work. Furthermore, this review also presents the current operations and future trends on some heavy oil EOR projects in Canada, Venezuela, USA and China.
This review showsthat the offshore heavy oilfields will be the future exploitation focus. Moreover, currently several steam-based projects and thermal-NCG projects have been operated in Emeraude Field in Congo and Bohai Bay in China. A growing trend is also found for the in-situ combustion technique and solvent assisted process both in offshore and onshore heavy oil fields, such as the EOR projects in North America, North Sea, Bohai Bay and Xinjiang. The multicomponent thermal fluids injection process in offshore and the thermal-CO2and thermal-chemical (surfactant, foam) processes in onshore heavy oil reservoirs are some of the opportunities identified for the next decade based on preliminary evaluations and proposed or ongoing pilot projects. Furthermore, the new processes of in-situ catalytic upgrading (e.g., addition of catalyst, steam-nanoparticles), electromagnetic heating and electro-thermal dynamic stripping (ETDSP) and some improvement processes on a wellbore configuration (FCD) have also gained more and more attention. In addition, there are some newly proposed recovery techniques that are still limitedto the laboratory scale with needs for further investigations. In such a time of low oil prices, cost optimization will be the top concerns of all the oil companies in the world. This critical review will help to identify the next challenges and opportunities in the EOR potential of bitumen and heavy oil production in the post steam injection era.
We present a newly developed 3D inversion code for Towed streamer EM data utilizing the Gauss-Newton method. The code is designed and implemented on a standard cluster of nodes to handle large-scale inversions of the order 25 million unknowns. The corresponding Jacobian matrix of about 2 Tb is split over the subscribed computational nodes in order to reduce the memory consumption on each node as well as to reduce the computational time. This enables the use of the full Gauss-Newton method on this amount of data.
The forward modeling part is based on a parallelized integral equation formulation of the electric field. The forward and inversion grids cover the entire survey area including bathymetry and down to 5 km below the sea surface.
The performance is demonstrated with an unconstrained anisotropic 3D inversion on Towed Steamer EM data over a survey area covering a total of 5206 sq. km, acquired in the Barents Sea in 2014. The survey consisted of 38 parallel acquisition lines with a spacing of 1.25 km and an average length of 115 km. The selected number of data observations for this case was 505820 with a total of 6 frequencies in the range from 0.2 to 2.2 Hz, 7226 shot points and 16 receiver offsets. The inversion grid consisted of 13 million cells and extended from the water column down to 5 km below the sea surface. The inversion ran 14 Gauss-Newton iterations and converged to a misfit of 3.7% with a geologically feasible anisotropic resistivity model.
Presentation Date: Tuesday, September 26, 2017
Start Time: 3:05 PM
Presentation Type: ORAL
How Do We Accelerate Uptake and Fulfill the Value Potential of Intelligent Energy? Nordtvedt, Epsis; and T. Unneland, Chevron Summary The objective of this paper is to identify ways to accelerate the uptake and fulfill the value potential of Intelligent Energy (IE). We have analyzed past experiences to identify both ways in which IE has been successful and the improvements that could be made to add value across a broader scale amid the challenges of today's commercial environment. In this paper, assessments are given on IE implementations to identify practical ways in which we can expand deployment and deliver results more quickly, including the importance of collaboration and competition in the IE domain, and how longer-term business models and new organizational ideas could improve the industry's uptake of IE. We have identified two areas in which we believe changes to our approach could deliver significant benefits--through the expanded use of integrated work flows and shared subject-matter-expert (SME) services. We discuss the benefits and challenges of this integrated approach to solution design, work processes, technology, skills, and competencies. Field cases from two major operators are given as best-practice examples on advanced use of IE in the oiland-gas industry. Introduction After more than 10 years of IE initiatives, the industry has increasingly published lessons learned from the early years (e.g., Lilleng et al. 2012; de Best and van den Berg 2012; Dickens et al. 2012; Dhubaiki et al. 2013; Lochmann and Brown 2014; Gilman and Nordtvedt 2014). As IE moves into its second decade, the landscape is changing. The decline in oil price, the resulting pressure on costs, and the rise of unconventionals are just some of the changes that present both risks and opportunities for IE to flourish (Pickering and Sengupta 2015). IE solutions during the first decade focused mainly on new technologies, better use of real-time data, new applications to analyze and visualize data, improving the data foundation, and increasing collaboration. Frequently, this has led to an increase in operational complexity with an associated increase in personnel. Most operators took a technology-driven, functional approach to provide us with improved surveillance, analysis, and collaboration tools. This has driven us mostly toward developing better tools to improve existing work processes.
The objective of this paper is to identify ways to accelerate the uptake and fulfill the value potential of Intelligent Energy (IE). The paper is co-authored by a cross-industry group drawn from operators, service provides and product vendors, all of whom have been involved in the IE arena for 10 years or more. We have analyzed the past experience to identify ways in which IE has been successful, and improvements that could be made to add value across a broader scale amid the challenges of today's commercial environment. In this paper, assessments are given on IE implementations to identify practical ways in which we can expand deployment and deliver results more quickly, including the importance of collaboration and competition in the IE domain, and how longer-term business models and new organizational ideas could improve the industry's uptake of IE. We have identified two areas where we believe changes to our approach could deliver significant benefits, through the expanded use of integrated workflows and shared Subject Matter Expert services. We discuss the benefits and challenges of this integrated approach to solution design, work processes, technology, skills and competencies. Field cases from two major operators are given as best practice examples on advanced use of Intelligent Energy in the oil and gas industry.
This paper discusses the workflow for high-resolution model building and imaging of a broadband multimeasurement towed streamer survey over the Mariner field in the North Sea. The model-building strategy combines the complementary techniques of full waveform inversion (FWI) and reflection tomography to generate an accurate, high resolution and geologically consistent velocity model, using both refraction and reflection energy. The 3D deghosted and reconstructed wavefield generated by the generalized matching pursuit (GMP) algorithm is densely sampled in all directions, and provides the ideal input for imaging techniques such as Kirchhoff prestack depth migration (KDM) and high-frequency reverse time migration (RTM). The combination of such a high resolution earth model and broadband, densely sampled input data provides the significant benefits for both overburden and reservoir characterization in this setting.
Discovered in 1981, Mariner is a shallow heavy oil development field located in the East Shetland platform of the UK sector of the North Sea. It contains two main targets: the Heimdal sands within the Lista Shale formation and Maureen sandstone.
Houbiers et al. (2012) and Østmo et al. (2014) describe a number of challenges for seismic imaging over the Mariner field, including:
• The presence of high-velocity shallow channels with very small spatial scales, causing significant distortion and pull-ups of the underlying events.
• Mapping of the Heimdal sands, which consists of a complex, disrupted channel system of remobilized unconsolidated and uncemented sand and injectites. These sands are hard to image due to the low acoustic impedance contrast with the surrounding shale.
The impact of these features is highlighted on legacy towed streamer marine data sets, including a 2008 vintage shallow-tow survey. In addition, a small ocean bottom cable (OBC) survey was acquired in 2008 over a subset of the field. With the application of FWI, the OBC survey was able to map the high-velocity shallow channels (Houbiers et al., 2012). However, successful imaging of the Heimdal sands remained challenging due to the limited seismic resolution of this data set.
This paper presents an analysis on the potential of Enhanced-Oil Recovery (EOR) and its challenges in offshore environments. EOR experience gained in onshore and shallow offshore should be translatable to offshore, but common sense developed over years of exhaustive laboratory research, modeling based on our best understanding of recovery mechanisms and extensive onshore field experience must be redeveloped to adapt to the stringent demands of the offshore. We show how screening criteria and workflows recently developed can be adapted for evaluation of EOR potential in offshore environments. A quick review of some of the new vibrant offshore basins is presented.
Offshore EOR decision-making and design require integrated operations that merge more tightly traditional IOR, for efficient flooding, and EOR, to increase overall recovery factor. Screening criteria can be integrated through more adequate consideration of soft issues. The starting point of the needed mindset is the understanding of soft issues that harden to become barriers in the offshore. Large well spacing, limited space and its cost and unmanned operations are apparent constraints. However, more subtle aspects drive the EOR designer's mindset. The primary injectant in the offshore is seawater and its main derived challenge its proper disposal or reutilization after breakthrough. Close-cycle operations impose further understanding of the consequences of EOR downstream.
We show that opportunities abound, but disruptive technologies must be evaluated to overcome issues of reservoir characterization, but we also need deeper understanding of geochemistry and rock-fluid interactions as enablers of close-loop production. Production acceleration as a vehicle for upfront investment mitigation demands more-than-usual IOR through conformance. A number of examples of successful strategies offshore show that some of the challenges can be overcome.
The results of this analysis should serve to rank opportunities in a number of basins. The current market provides opportunities, but a more rigorous analysis of opportunities is required for their evaluation.
Berg, Eirik A. (Statoil ASA) | Reksten, Kari (Statoil ASA) | Scott, Anthony Stephen John (Statoil) | Ibatullin, Tair (Statoil ASA) | Møllerstad, Hilde (Statoil) | Aasum, Yngve (Statoil ASA) | Julseth, Lillian (AGR Petroleum Services)