Applications of Electric Logs and Geomechanical Models to Optimize Drilling and Well Completions in the Burgos Basin

Abstract

Electric logs and borehole imaging were used to build a geomechanical model to predict wellbore instability during drilling and to optimize casing designs and completions to control sand production in the Burgos Basin. This paper describes how geomechanical models can explain several problems in drilling and completion during the development of some of the fields in Northern Mexico. The total stress tensor model, the pore pressure model, and the mechanical properties model are discussed. Validation of the model is a critical step before it can be applied to design new wells. The geomechanical model was used to design a new well and to optimize drilling, completion, and production techniques for the reservoir. The model was used to optimize the placement and orientation of perforations, evaluate proposed hydraulic fracturing designs, and select the critical draw-down to produce a well. Actual drilling, completion, and production events for the new well were analyzed, and conclusions about how the geomechanical model supported the complete design are also included in this paper. Introduction Several studies worldwide have confirmed that the optimization of non productive time related to borehole instability while drilling, the determination of the preferential permeability in naturally fractured reservoirs, the integrity of seals in geological faults, sand production potential, reservoir compaction and casing damage, are controlled by the geostatic in situ stresses, the pressure of the fluids in the pore spaces and the mechanical properties of the rocks. A geomechanical model for the field was built based on information from conventional and electric imaging logs in addition to the drilling information of the first exploratory well, F-1, drilled in the field. The model was validated predicting breakouts in the F-1 well and comparing them with rock failures observed in the caliper log, breakouts observed in the electric imaging log and with drilling problems related to wellbore instabilities. The geomechanical model for the field predicts well the observations and problems identified in the F-1 well during the drilling, completion (hydraulic fracture) and initial production of the well. A wellbore stability analysis during drilling and completion was performed for the F-1 well to predict the mud weight requirements during drilling to prevent large breakouts/washouts or lost of circulation problems and the required borehole pressure to prevent sand or formation flowing during the production phase. Furthermore, the lessons learned from F-1 were successfully applied to drill, stimulate and produce a new well, F-101. Geomechanical Model The project started collecting all the information related to planning, drilling and completion of the F-1 well. This well was drilled as a directional J-shape well to reach the final objective in the Jackson Formation, as presented in Figure 1. General information of the Field was reviewed (including surface seismic and maps), the structural model, standard and advanced wireline logs including dipole sonic and images acquired in the F-1 well, drilling and completion information (including daily reports, mud weight reports, well design schematic, leak off tests and Minifrac tests), pore pressure measurements in the reservoir, well geometry and formation tops.