It’s often best to make “informed” decisions when resolving challenges. The information necessary to assist the process, although available through numerous channels, sometimes is uselessly bypassed or avoided for unknown or indefensible reasons. Often, it is not until long after the process or challenge has subsided that a historical perspective brings to light the fact that, had all available information been utilized, a more fruitful outcome could have been accomplished.

A similar review of an exploration strategy is required as the industry adjusts to continue effective exploration under a reduced budget.

Potential field methods and remote sensing technology have been widely used in the E&P process for decades, and the use of such data continues successfully today. Electromagnetic, magnetic and conventional gravity data, along with hyperspectral imagery and radiometric methods, are some of the most commonly used techniques. However, a more advanced gravity mapping process has gained significance over the past decade and has provided an enhanced subsurface picture for oil and gas exploration: gravity gradiometry. This high-resolution broadband mapping technique was initially developed by Lockheed Martin for military use and has since been declassified and made commercially available for hydrocarbon and mineral exploration. The data can be rapidly acquired with aircraft or vessels. The resolution attainable places the technique into direct and useful relevance to the design, processing and interpretation of the seismic survey.

ARKeX has been acquiring broadband gravity using full-tensor gravity gradiometry (FTG) instrumentation in combination with a scalar gravity sensor for more than a decade now, but the adoption challenge remains a large hurdle. Specific to the challenge is how to get oil and gas companies to recognize the comprehensive benefit of a broadband gravity measurement and commit budget to it at the optimal point in their exploration process. Technically, a multisensing approach that provides information on the rock’s density and velocity properties makes perfect sense (who would want one’s medical practitioner to run just a single test for a medical diagnosis?). In terms of risk, companies like ARKeX need to demonstrate that there is a clear and quantifiable value proposition available to those prepared to challenge a paradigm and that this delivers a distinct benefit that outweighs the cost and risk of making such a change.

ARKeX depends on an effective coaching process, relying on previously successful surveys to demonstrate the quality of the data to qualify its assertions that altering the timing and scale of broadband gravity surveys will enhance the effectiveness and efficiency of the whole exploration process. As exploration moves into its new budgetary cycle, the development of efficient practice seems to be imperative. So how is it done?

Timing
Timing is ably demonstrated by case studies in the East African Rift, where the cost and logistical load associated with seismic acquisition and drilling drives a strong incentive to get those surveys right the first time. Operators have exploited the well-publicized attributes of broadband gravity surveys—including a low cost, low environmental impact and rapid and accurate results—to the extent that gravity data acquired using FTG instrumentation are becoming accepted as a valid work commitment associated with exploration licensing rounds. Similar opportunities are now available in West Africa and the Caribbean.

Scale
How is the question of scale addressed? Fundamentally, large-scale imaging offers two benefits. Clearly, operational costs are diluted as benefits of scale become available. More importantly, though, and on a key technical point, spectral continuity at long wavelength allows proper defendable quantitative interpretation of a deep structure without the ambiguity associated with edge effects and survey merges. In asking for the adoption of comprehensive surveys, explorationists are being asked to take a leap that involves prominent invoices associated with acquiring data that may be outside a licensed area. Geology, and more importantly its response to remote sensing technologies, does not stop at license block boundaries. Ideally, a case study is needed that illustrates this aspect of the value proposition; the majority of surveys to date are not large enough to provide a positive example, but several are in preparation.

One such case will be the environmentally sensitive U.S. East Coast, where hard work resulted in an award of the first geological and geophysical license in more than 30 years to probe this area. ARKeX spent a considerable amount of time in preparation and presentation to the Bureau of Ocean Energy Management (BOEM) and then applied for one of the nine geophysical permits to explore off the east coast ahead of the planned Outer Continental Shelf lease sale in 2021. In July 2015 ARKeX was awarded the permit to commence a multiclient FTG program specific to the offshore areas of the exploration-friendly states of Virginia, North Carolina and South Carolina. Here, scale is a necessary attribute as the broadband gravity data will be instrumental in defining both the licensing strategy and the seismic campaigns that will follow.

Unfortunately, industry funding is slow in coming as a result of a few key influences. One is the apprehension from the E&P sector that the seismic permits (for proposed multiclient programs) will still not be granted due to issues with the National Marine Fisheries Service and its incidental harassment authorizations. This will be mitigated with the realization that a responsibly designed “right first time” seismic program will minimize disturbance to the environment, cost to the exploration companies and inefficiency for the seismic companies. It should be noted that the broadband gravity won’t replace seismic data. It can, however, be complementary and beneficial when coordinated with seismic programs, so any notion that by awarding ARKeX its permit, BOEM can put the others aside is erroneous.

Another potential impediment is the obvious curtailing of capex by E&P companies for discretionary expenditure on exploration
programs that won’t deliver value for a few years out, and this represents another instance of the timing paradigm. Offshore exploration, particularly 2-D seismic, has a proportionally smaller incentive to optimize the efficiency of a line plan when compared with its onshore counterpart. If the viewpoint of proportionality is abandoned and consideration is instead given to the absolute savings associated with avoiding sub-optimally positioned seismic lines, whether onshore or offshore, a real efficiency gain can be demonstrated. Clearly the efficient and properly designed survey also will be the one with the smallest environmental footprint.

In conclusion, ARKeX continues to work hard to provide asset teams with the collateral they need to procure, acquire, process and incorporate broadband gravity data into their E&P processes. Numerous successes over the years and around the world are a testament to the technical and commercial benefits of such technology.