Evaluating Mexican Deep Water Turbidites

Abstract

Summary Exploration evaluation for deepwater Mexican reservoirs requires strategic investments and optimal data acquisition to build geological and petrophysical models of the sub-surface in presence of formation anisotropy, thin-beds, and complex fluids distribution for optimal field development planning. This presentation will focus on the common wireline acquisition strategies that are used to evaluate Mexico turbidite formations where low resistivity pay and synthetic oil-based mud are used to drill the wells. A complete petrophysical evaluation integrates state of the art wireline technologies for true sand resistivity with lithology, porosity and permeability to better characterize the laminated vs dispersed clay distribution for an accurate reservoir summation. Combining the acoustic and borehole images for velocities (geomechanical applications) and using downhole in-situ stress testing techniques gives a more detailed understanding of depositional architecture and distribution of reservoir facies and flow units. Today, we use focused sampling techniques to better understand in-situ fluid characterization and achieve much cleaner and faster formation samples. The higher quality samples (low OBM contamination) are required for achieving the most accurate PVT, flow assurance, water compatibility, and crude analysis to optimize the “get it right the first time” large field development investments. In Mexico, Interval Pressure Transient Testing (IPTT), combined with downhole in-situ fluid analysis (DFA) are used to assess reservoir characteristics layer by layer. This applied work flow methodology is an important input for the Reservoir Fluid Geodynamic (RFG) study to resolve and minimize the uncertainties of the reservoir architecture and de-risk future developments. Other technologies deployed during the Wireline acquisition program include a Mechanical Sidewall coring program and the VSI (Vertical Seismic Imager). The Mechanical Sidewall coring tool is used to for depth correlated extraction of core samples in reservoir and non-reservoir rocks formations. This tool has successfully acquired sidewall cores in low UCS rock strength and samples are used for rock and permeability analysis. This service complements the full conventional core program by allowing additional samples to be taken where whole core is not required. Finally, in areas where there is uncertainty in the surface seismic, the VSI (Vertical Seismic Imager) is used to acquire a borehole seismic with Zero Offset or Walkaway surveys. The borehole surveys provide accurate determination of formation tops and are used for further calibrating the reservoir model versus the surface seismic. Turbidite and low resistivity formations are much better understood with the application of industry proven technologies. This presentation will discuss the Mexico workflow and methodology and application of these measurements to maximize the understanding of these special reservoirs located in the Mexico offshore waters.