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Hite D.A.,EMGS | Hiner M.,Sierra Hamilton Engineering | Solevag L.P.,EMGS
Proceedings of the Annual Offshore Technology Conference | Year: 2015

It's been over a decade since the first CSEM acquisitions were done along 2D lines in relatively open water. Today's CSEM acquisitions cover hundreds of square kilometers in true 3D fashion using receivers and towing systems purpose-designed for ease of handling, accuracy of deployment and efficiency in towing. Making use of these advancements, EMGS has been able to acquire data closer than ever before to existing infrastructure in a safe and reliable manner. This paper covers the acquisition of a portion of the multi-client survey Daybreak Phase III around the Perdido installation over the Great White field in the Alaminos Canyon protraction area of the U.S. Gulf of Mexico. The survey covers approximately 46 OCS Blocks in water depths from 1700-3000m. The survey was acquired by the vessel EM Leader during the month of June, 2014 and consisted of 130 receiver drops and 702 tow kms. In order to acquire the survey, EMGS contacted Shell, the operator of Perdido, and requested permission to conduct operations around the facility. Shell agreed and provided the following stipulations which were to be complied with at all times: When the planned tow line crosses a pipeline location, the CSEM source must be raised from its nominal towing depth of 30m to 100m at a point 250m away from the pipeline No gear or the survey vessel could come within 1.5 NM of the facility The survey area bathymetry and infrastructure are showin in Figure 1. Copyright © (2015) by the Offshore Technology Conference All rights reserved.

Gabrielsen P.T.,EMGS | Abrahamson P.,MultiClient Geophysical | Panzner M.,EMGS | Fanavoll S.,EMGS | Ellingsrud S.,EMGS
First Break | Year: 2013

There is new and growing enthusiasm for hydrocarbon exploration in the Barents Sea after three recent discoveries: Skrugard, Havis, and Norvarg. We demonstrate how using wide-azimuth 3D controlled-source electromagnetic (CSEM) and 2D seismic data together can improve the identification of prospective areas in the region. An interpretation workflow is presented to show how the challenging resistivity background in the Barents Sea is handled. To do this, we introduce a new inversion attribute called the anomalous vertical resistivity. The inversion attribute is co-visualized with 2D seismic data and used to estimate recoverable reserves. The workflow is illustrated on both synthetic and real data for the Skrugard and Havis discoveries. Both discoveries are identified on CSEM maps and by integrating CSEM data with seismic data. In addition, a new lead is identified. We show that CSEM data carries structural information and that the horizontal resistivity trends can be used with 2D seismic data and well logs to interpret the distribution of good-quality sands. Hydrocarbon reserve calculations based on the 3D CSEM data for the Skrugard and Havis discoveries have P50 values consistent with the publicly available reserve estimates. The reserve estimate for the new lead also shows significant potential. © 2013 EAGE.

Hesthammer J.,Rocksource | Stefatos A.,Rocksource | Boulaenko M.,Rocksource | Fanavoll S.,EMGS | Danielsen J.,EMGS
Leading Edge (Tulsa, OK) | Year: 2010

During the past several years, we have seen an increasing focus on the use of CSEM technology for hydrocarbon exploration in marine environments and, recently, a number of success stories have been published. The technology has been demonstrated to aid both detection and delineation of hydrocarbon-filled reservoirs. © 2010 Society of Exploration Geophysicists.

Baltar D.,EMGS | Roth F.,EMGS
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

Net rock volume is the main uncertainty affecting the evaluation of recoverable reserves for prospect risk analysis. We present a Monte Carlo method for estimating a net rock volume probability distribution from an anisotropic 3D CSEM inversion result. Given a CSEM favourable exploration setting, the method can significantly reduce the uncertainty in net rock volume, especially for stratigraphic traps. The method relies on the sensitivity of CSEM to the volume of resistive rock and on the transverse resistance equivalence principle for relating the low resolution inversion result to possible reservoir scenarios at the well log scale. We demonstrate the performance of the method using unconstrained inversion results from a full-azimuth 3D CSEM survey over a known oil field. No prior information in terms of well data or field geometry was assumed to simulate an exploration case. The uncertainty associated with the resulting net rock volume probability distribution as measured by the P10/P90 ratio is less than 6, which is considered low by common industry practice. The actual net rock volume defined by the reservoir top and the oilwater contact coincides with the 60th percentile of the distribution, i.e. the predicted range of possible net rock volumes is very reasonable.

Morten J.P.,EMGS | Kumar K.,EMGS
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

We have simulated a salt flank hydrocarbon reservoir imaging case using the 3D controlled source electromagnetic data from the SEAM phase I model. The complication due to the dominant EM response from the salt body is tackled by a structural constraint. In our simulated exploration scenario, we assumed that seismic imaging provided information to construct an approximate salt structural model but with three types of errors: 1) Limited information below salt overhangs and no base salt, 2) inaccurate lateral and depth positioning, and 3) incorrect salt resistivity. A modeling study and our imaging results demonstrate that the applied workflow is robust against these errors, and the 3D inversion results in a reconstruction that agrees well with the true model reservoir laterally and in depth.

Frenkel M.A.,EMGS
PIERS 2010 Cambridge - Progress in Electromagnetics Research Symposium, Proceedings | Year: 2010

The marine Controlled-Source Electromagnetic (CSEM) method has been evolving into a subsurface resistivity imaging tool for increasingly complex geological settings. The measured EM field needs to be inverted to obtain accurate formation resistivity volumes. This information can be used to find reservoirs and determine hydrocarbon saturations. An important step in the resistivity interpretation process is the inclusion of constraints to guide inversion and reduce its non-uniqueness. In this paper, we use 2.5D and 3D synthetic models to investigate the accuracy of the subsurface resistivity reconstruction using additional information about the target body's position. We show that application of seed-type initial models leads to a significantly improved inversion-based CSEM resistivity interpretation.

Ellingsrud S.,EMGS
76th EAGE Conference and Exhibition 2014, Workshops | Year: 2014

CSEM was established as an industry 12 years ago by several service companies that offered 2D CSEM commercially. The presentation will focus on how CSEM has developed as a commercial tool since the first commercial introduction 12 years ago and look into the future. The technology has gone through a significant development. The most important step was from 2D to 3D wide azimuth data enabled by improvements in equipment, operations, inversion and streamlined processing oflarge data volumes. Both horizontal and vertical resistivity cubes are now inverted, enabling mapping of anisotropy and CSEM is no longer limited to deep-water applications. Wide-azimuth 3D surveys will most likely be the main way to acquire CSEM data also in the future. In future processing and inversion, magnetic field data will be used more to improve imaging, especially in shallow water. In general MT data will also be used more which implies stationary seafloor receivers with both electric and magnetic sensors (Ex, Ey, Hx and Hy). CSEM will see deeper (stronger sources), get better resolution and improved data will be processedjointly with seismic, resulting in improved imaging. Moreover, the data will be used as an important part in the oil companies workflow.

Mittet R.,EMGS | Morten J.P.,EMGS | Jensen H.R.,EMGS
76th EAGE Conference and Exhibition 2014, Workshops | Year: 2014

The marine controlled-source electromagnetic method (CSEM) can detect subsurface hydrocarbon reservoirs because they represent resistors in a conductive medium, i.e. brine-saturated rocks. The limitations on the applicability of the technology are given by target burial depth, lateral extent, and the net pay thickness. Improvements to the acquisition instrumentation can extend the applicability and increase the resolution. However, several factors affect the accuracy of the measured data. To achieve a significant improvement it is important to understand the experimental error contribution from each hardware component in relation to the target effect on the data. We present error propagation analysis for CSEM acquisition, which reveals feasible limitations for target detection. Further, we show how equipment can be optimally improved to extend applicability of the technology.

Ellingsrud S.,EMGS | Ridyard D.,EMGS
First Break | Year: 2012

As EMGS passes its 10th birthday, we believe there will be plenty of late adopters who have yet to harness the value of EM technology. However, in our view the mainstream of the E&P industry is now using 3D EM where it can be shown to have value. It follows that the introduction of more applications and new technology developments that marine EM will continue to broaden its market niche over the next 10 years. © 2012 EAGE.

Fanavoll S.,EMGS | Gabrielsen P.T.,EMGS
76th EAGE Conference and Exhibition 2014, Workshops | Year: 2014

After more than ten years of acquisition of EM data, it is widely accepted that the technology has a significant potential for improving exploration efficiency. However, despite the fact that there is a convincing track record of EM results correlating with well results and some oil companies incorporating EM technology into their workflows, adoption of the technology in the industry overall has not come a long way. This paper discuss some of the challenges faced by the petroleum industry in the interpretation of EM data, as well as necessary improvements of the technolgy in order to enhance the value of incorporating EM data into decision workflows. the current use ofEM is illustrated by two examples, one unsuccessful and one successful.

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