Seismic acquisition using autonomous vehicles: A game changer for the E&P oil and gas industry

In the application described here, an autonomous marine vehicle (AMV) is equipped with a 3D seismic sensor array (3DSA). The 3DSA consists of 15 hydrophones mounted on cubic frame of about 1 m in size. Various field tests and commercial projects have been conducted using autonomous vehicles as platforms, each towing a 3DSA. Often, these have been deployed during ongoing traditional seismic surveys, thus allowing the possibility of making direct comparisons of operations flexibility and data. The objectives of this project were to · Assess the feasibility of seismic acquisition using AVs and 3DSA, including safe deployment and retrieval · Evaluate the performance of the 3DSA based on holding station capability, maintenance of desired depth, and accuracy of measurements of pitch and orientation · Compare the quality of the acquired seismic data with the pressure data recorded in the traditional surveys Marine seismic data are normally acquired using towed-streamer arrays, ocean-bottom cables (OBC), or ocean-bottom nodes (OBN) where the receivers are in fixed positions on the seafloor. Towed streamer-acquisition is the predominant method of marine acquisition because it is highly efficient and easy to implement. Narrow-azimuth (NAZ) streamer acquisition geometries typically acquire good-quality seismic data in noncomplex geologic environments and have a very well-established processing methodology. However, water depth, seafloor topography, or operational constraints due to in-situ infrastructure and obstructions can make acquiring data using these methods difficult and could result in a decrease in operational efficiency, which would increase acquisition cost or result in poor or zero data coverage. For seismic applications, the 3DSA consists of 15 hydrophones (3 in each of the five arms) mounted on a frame approximately 1.5 m in size. A buoyancy engine just below the top arm ensures that this arm remains on the high side and that the entire array is oriented and does not rotate on its axis while moving through the water. The 3D sensor array continuously records seismic data as well as array orientation and depth data. Autonomous marine vehicles provide several unique capabilities for acquiring data in marine environments. Their low cost compared to conventional vessels allows deploying them in tandem over defined areas to yield comparable results and complete coverage. In the last few years, the oil and gas industry has seen the use of AMVs grow from a level of infancy to full maturity and become an essential part of the offshore exploration and production toolbox. The vehicles are rapidly evolving in response to the needs of the industry, particularly in challenging environments, frontier areas, extremely shallow waters and prospecting close to obstructions. Projects in Abu Dhabi and the US Gulf of Mexico demonstrated the successful and safe deployment, seismic data acquisition, and retrieval of the AVs and 3DSA. The evaluation criteria indicated the consistent performance of the 3DSA and that the AMV-acquired data are comparable to conventionally acquired data in signal-to-noise ratio and frequency bandwidth.