Combining Ultra-Deep Resistivity for Landing and Horizontal Sections to Maximize Reservoir Exposure in Complex Clastic Reservoirs Utilizing High Definition 1D and 3D Inversions

Abstract Prior to drilling the horizontal reservoir section of any well, a landing section is usually drilled to place trajectory of the well in the target zone. Selective logging-while drilling (LWD) sensors such as gamma ray, resistivity, density and neutron porosity may be considered to be used while drilling the landing section. Conventional LWD sensors have a limited depth of investigation (DOI) when compared to LWD reservoir mapping sensors. This paper presents the advantages of utilizing ultra-deep resistivity (UDR) tools to improve the landing practices and improve the well placement efficiency in the following horizontal sections. Prior to drilling landing section intensive and comprehensive pre-well analysis is performed in order to identify optimal ultra-deep resistivity tool setting and frequencies for the purposes of getting most informative 1D and 3D inversions. Azimuthal ultra-deep resistivity tools along with triple combo logs have been utilized while drilling landing sections for multiple wells in complex clastics environment. Intensive analysis of ultra-deep resistivity data has been done and showed the optimum settings of the tool frequencies and transmitter-receiver spacings to successfully map the target zone at the maximum possible distance. High definition 1D and 3D inversions were used and provided valuable information for optimizing the landing strategy as well the well placement of the lateral section. Ultra-Deep resistivity tools were able to map target higher resistive zone at distances higher than 50ft TVD away from the wellbore starting 75deg wellbore inclination. In addition, advanced ultra-deep resistivity inversion algorithms allowed the mapping of 6 distinct laminated low and high resistivity zones of variable properties and thicknesses. Target zone structural dip angle and thickness was identified while drilling allowing the well trajectory to be optimally placed in the target zone with the optimum hole inclination and to prevent accidental reservoir exit or unnecessary excessive drilling footage. LWD log responses of the drilled intervals have also confirmed the ultra-deep resistivity inversion response. Intensive analysis for the 3D inversion data improved reservoir insight revealing structural displacements in the target zone. All of this information were then used to optimize the strategy for the lateral well placement and as a result both laterals has been successfully geosteered in target zones of complex clastics reservoir with high net-to-gross ratio (NTG). This paper describes an improved horizontal well landing practices allowing to successfully map and place the wells in the target zones and optimizing the well placement of the horizontal sections.