TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractOver 100 horizontal laterals averaging 4,600 feet in length have been drilled in a shallow, heavy oil reservoir in Eastern Venezuela. Measurement While Drilling (MWD) continuous directional measurements and Logging While Drilling (LWD) azimuthal measurements are used to steer the wells through the reservoir, along a specific well path chosen from vertical stratigraphic wells for each pad and 3 Dimensional (3D) seismic which covers the field area. Experience from drilling the horizontal wells has shown that this reservoir is laterally discontinuous between the vertical stratigraphic wells and that this discontinuity is not always predicted from the surface seismic. However, the LWD azimuthal measurements, presented in the form of a 3D image is able to give the orientation of the wellbore relative to the geometry of the channels. Another use of the azimuthal images is to identify the numerous shale stringers that are only a few inches thick. These stringers are not detectable on the vertical stratigraphic wells due to the limited bed resolution of the wireline logging tools run in these wells. These stringers in the laterals greatly reduce the non-azimuthal resistivity measurements and give a false indication of an approaching reservoir bed boundary.

More than 50 horizontal laterals averaging 4600 feet in length have been drilled in a shallow, heavy oil reservoir in eastern Venezuela. Precise navigation through the formations was necessary to optimize placement of the lateral drainholes and maximize the percentage of reservoir sand exposed. To meet this requirement, an optimized bottom hole assembly (BHA) design and logging while drilling (LWD) interpretation technique were developed based on field experience. Measurement while drilling (MWD) continuous directional measurements were used to steer the well through the reservoir, along a specific well path chosen from three-dimensional (3D) seismic that covers the field area. The LWD azimuthal and bit electrode measurements were integrated with the 3D seismic to allow an interactive interpretation of the stratal boundaries present within the reservoir which resulted in continual refinements to the planned well path. Using the information derived from the LWD azimuthal and bit electrode measurements, the location of shale stringers, bed boundaries, and pay sand relative to the BHA could be determined and the well then steered in the appropriate direction to maintain an optimum position within the oil reservoir. As a result, the number of sidetracks was reduced and the percent sand encountered increased. The longest horizontal lateral in Venezuela was also drilled and completed as part of this project.