Improving Drilling Success by Integrating Sedimentology and Diagenesis models: Case Study from South America

Abstract

Summary The improvement of the success of the well drilling is an important task during the development of hydrocarbon reservoirs, and the use of three dimension mechanical earth model (MEM) is key to predict the behavior of drilled well and to prevent damaging the well. The MEM encapsulates several information related to pore pressure, mechanical properties of the reservoir rock, the geometry of the reservoir limits and the overburden and the stress regime. Various workflows were proposed to build and update the MEM. However, those approaches do not incorporate the complexity of the carbonate rocks. In fact, the carbonate rocks, hold heterogeneous pore systems that impact the rock strength and the pore pressure behavior. The heterogeneity of the pore systems is due to the specificity of the deposition process of the carbonate rocks, mainly composed of fauna and or flora, and the rate of diagenesis. In this paper, we propose a workflow that improves the modeling of the mechanical properties for carbonate reservoirs. This workflow starts by reconciling data at different scales, diagenesis rate at thin-section scale, scratch and laboratory strength tests at plug scale, electrical logs at well scale, and three dimension sedimentology and seismic volumes at reservoir scale. The second step is to establish the relationship between the mechanical properties, the pore pressure, the seismic attributes, the sedimentology and the rate of diagenesis. The last step allows interpolating and assessing the uncertainty of the mechanical properties and pore pressure in the three dimension reservoir model. The workflow was applied to an off-shore carbonate field in South-America. It showed that there is a strong relationship between the type of fauna and flora, composing the carbonate rock, and the rock strength and pore pressure. The three dimension mechanical model, at hundred meter horizontal resolution and one foot vertical resolution, allowed to quantify the risk associated with the drilling of the previously planned wells, to improve the location for future drilling wells and to optimize the drilling parameters such as mud weight.