Maintaining and increasing production are the main challenges for oil and gas companies in today's difficult market. To achieve these goals, these companies are looking for new techniques to improve fracture characterization. Open natural fractures, when present, can provide the conduit for the majority of natural gas in low porosity, hard rock environments. Therefore, a complete understanding of fracture attributes is required for optimal production, as well as cementing and completion design, well placement, and reservoir modeling.In the La Paz field in Venezuela, previous petrophysical interpretation assumed the cementation exponent, m to be equal to 2. This assumption was made due to the absence of special core analysis and logging information such as dipolar sonic and micro resistivity image logs, increasing the uncertainty in the petrophysical model.Using the crossplot of Ø vs. Rt on log log coordinates it was possible to determine the cement exponent, m, value for each zone. This parameter was fundamental to the estimation of the fracture and matrix porosity, fracture Intensity Index, and the Partitioning Coefficient.The methodology applied in this case study is based on advanced acoustic analysis integrated with triple combo and borehole micro resistivity images. The triple combo (gamma ray, induction resistivity, neutron and density) and the image data allowed identification of the natural fractures, and the Stoneley wave analysis confirmed that several of the fractures observed in the borehole image data were open.This methodology reduced the fracture characterization uncertainty of the La Paz Field and helped to more accurately estimate petrophysical properties where special core data is not available.

Volumetric estimates are required at all stages of the field life cycle. One of the main parameters used to estimate the stock tank oil initially in place is the water saturation, which depends mainly on the true resistivity (Rt) of the formation. Correct log interpretation of LWD resistivity is a challenge in the Zuata Field due to the apparent conductive invasion profile phenomenom. This study compares the LWD phase resistivity against Compact™ Dual Laterolog resistivity curves in the same well. The section of the well was drilled with water-based mud (WBM) in unconsolidated sandstones intercalated with shale and low conductivity formations. The geological information for this area (core analysis and image log from two neighbor wells) indicates that there are sand/shale laminations in the surrounding formation. The area where significant differences were observed among the LWD propagation resistivity curves coincided with spiral-shaped wellbore. The interbedded formation causes the electrical anisotropy and the spiral zones amplify this effect. Compact Dual Laterolog tools on the contrary, although affected by anisotropy, can be easily borehole correted to yield an accurate Rt value. In conclusion, when the LWD data can be correctly normalized the anisotropy effect could be reduced and the LWD propagation resistivity curves may be use for formation evaluation; however, another option is to run tools that can be properly corrected by borehole size and are less affected by anisotropy and polarization such as the Compact Dual Laterolog MDL.