A High Resolution Seismic Study in the Gulf of Mexico
Authors: Salter Richard , Moldoveanu Nick , Hultzsch Paul 
Published: October 2008

In seismic exploration and field development of the Lankahuasa area offshore Mexico, a concerted seismic analysis and an integrated reservoir characterization approach have provided valuable information in explaining differences in well performance. In this paper, we present a fully integrated approach that combines Q seismic survey evaluation and design (Q-SED), high-quality seismic acquisition with a significantly enhanced signal-to-noise ratio and greater bandwidth and advanced data processing to maximize the usefulness of the data. These data were then analyzed through an integrated reservoir characterization workflow that utilized a combination of quantitative property prediction from prestack full-waveform inversion with qualitative attribute analysis. Numerous attributes were generated along with several inversion volumes.

This analysis provided an understanding of the structural and stratigraphic relationships between two wells that had not been possible to interpret using conventionally acquired and processed seismic data. The ability to map sand bodies to a thickness resolution of 12 to 15 m compared to over 30 m previously available enabled a high resolution and accurate prediction of reservoir properties. Evidence of heavily fractured and faulted zones around the two wells provided important input in terms of well planning and drilling hazards.

This study resulted in the subsequent successful relocation of a planned sidetrack from the discovery well to avoid structural features not previously interpreted.

Introduction

The Lankahausa Q proof-of-concept (POC) survey was acquired in January 2003.

This survey was shot for the purpose of:Comparing with an earlier conventional 3D seismic survey shot at the same location in 1999.Improving the amplitude fidelity and vertical resolution to accurately delineate prospects previously defined. The required frequency bandwidth to image the thin layers is 3-95 Hz. The frequency content of the legacy dataset could not image the thin-layer reservoirs at a depth of 2.0- 2.8km.Interpreting and characterizing the reservoir units (primarily Arenas 3, 5, and 10) in terms of structural and stratigraphic complexity in addition to reservoir property prediction and distribution. The acquisition parameters, the processing sequence and the initial understanding of the objectives of the survey are based on a survey evaluation and design (SED). Data processing involves technologies unique to this highresolution seismic data that define reservoir geometries better than conventional data, and are also more reliable. The Reservoir Services (RS) project team evaluated, analyzed, and interpreted the data while maintaining contact with key Petroleos Mexicanos (PEMEX) management and technical staff to ensure it was not overlooking any of the known reservoir issues at Lankahuasa.

This paper describes the major steps taken in this case study and illustrates the key reservoir features that are only visible when advanced processing is applied to high quality seismic data.

Data analysis and interpretation were integrated with the processing where possible so that the final analysis was completed by end March 2003. Fast turnaround was a prerequisite for this study due to the need to impact on further exploration and development of this field area.