3-D Geomechanical Modeling and Wellbore Stability Analysis in Abu Butabul Field

Abstract

Abu Butabul Field is located within onshore Oman Block 60 in the Western region of the Central Oman Desert (Figure 1). Gas-condensate was discovered in the field in 1998. The main reservoir is the Cambro-Ordovician clastic Bank formation, which is buried over 4200 m below sea level with very low porosity and permeability. Wellbore instability related drilling problems were encountered while drilling most of the appraisal wells in the field. The problems were mainly in the shallower Natih and Nahr Umr formations, Gharif formation and deeper Safiq, Ghudun and Mabrouk formations. A geomechanical modeling study was conducted in the field to understand the causes of the wellbore instability problems and to provide recommendations for drilling new wells. Data from nine wells were analyzed and used for the construction of 1-D mechanical earth models. Rock mechanical testing data on core samples and pressure and stress memasurement were integrated in the models. Wellbore stability analysis of those wells provided insight into the causes of the wellbore instability problems. To predict wellbore stability at any location in the field more efficiently and capturing the lateral formation property variation as indicated by the seismic data, a 3-D geomechanical model was constructed and subsequently used for predicting wellbore stability for new wells to be drilled in the field and hydraulic fracturing pressures for fracturing stimulation of horizontal wells. This paper describes the process of constructing the 1-D mechanical earth models, performing wellbore stability analysis for the appraisal wells, Integeration of 3D seismic Inversion, constructing the 3-D geomechanical model, predicting wellbore stability for new wells using data contained in the 3-D model and post-drill wellbore stability analysis of the planned wells.

3D Geomechanical Model Construction for Wellbore Stability Analysis in Algerian Southeastern Petroleum Field

“…Therefore, we were able to proceed to 3D geomechanical model construction. The workflow of this process is summarized in Figure 7 ( [6,[27][28][29][30]).…”

“…When building a 3D geomechanical model, the first step is to create the grid in which the computation of the constraints will be carried out [31]. The grid is guided by the geological model of the region and must contain the overlying layers in addition to the reservoir's layers ( [6,32]). As the acoustic impedance volume was obtained from the seismic inversion results, a simple calculation was used to deduce the volume of the acoustic velocities, as shown in Figure 5a.…”

“…The study region in this research work was in the southeast of Algeria, and seismic inversion and a 3D geomechanical model were employed using seismic and well-logging data [5]. In order to emphasize the various lithologies and characterize the reservoir, the seismic data were first inverted before being exploited [6][7][8]. The amplitude versus offset (AVO) model was build based on Roy White's methodology and retrieved using Aki and Richard iterative approximation [9].…”

Formation Susceptibility to Wellbore Instability and Sand Production in the Hajdúszoboszló field, Pannonian Basin: Hungary

“…Wellbore instability occurs as a result of excessive stress concentrations around the wall of a borehole often induced by inadequate mud support during drilling operations (Qiuguo et al, 2013). The earth's in-situ stresses are caused by overburden weight, tectonic forces and pore pressure.…”

A Case Study for Evaluating Effective Geomechanical Parameters and the Influence of the Biot Coefficient on the Stability of a Wellbore Wall in the Asmari Formation using Machine Learning

“…Various factors such as in-situ stresses, formation rock strength, formation fluid pressure, drilling mud pressure and wellbore trajectory are involved in wellbore stability. Among these factors, wellbore trajectory and drilling mud pressure range are under our control and can be changed to prevent problems [12,13]. Mechanical processes in porous media (such as rocks) consist of 2 basic parts: Fluid flow and rock displacement.…”