SUMMARY: Directional drilling in fields bedding plane formations has become a challenge to the petroleum industry because of the complexity of its operations. Therefore, drilling geomechanics plays an important role in engineering planning and calculation prior to the construction of a wellbore which makes it possible to determine a possible instability of the rock formation associated to the drilling inclination of wellbore and inclination of preexisting bedding plane. This paper analyzes the effect of the attack of angle of drilling on the geomechanical wellbore stability of formations with weak bedding plane or laminations using a finite element model and the Abaqus® software considering the rock as an isotropic medium. Three analytic tests with different drilling angles were developed, allowing to establish relationship between the attack angle and wellbore stability. Variables such stress, deformation and failure in rock bedding plane during drilling were analyzed. The results show that at higher attack angles the greater the wellbore instability is associated with the presence of the weak bedding plane
During the drilling of hydrocarbon wells various types of rock and lithologic formations are drilled, including among them naturally laminated ones or bedding planes formations. These formations contain natural disorders that are called weak bedding plane, which represent a major operational challenge during drilling due to the characteristics of its surfaces with little or no cohesion between them. This causes a displacement and imminent separation of the surfaces, namely, unstable conditions when being altered mechanically with the cutting bit, generating slides and cavings into the wellbore which subsequently cause operational problems during drilling such as stuck pipe or loss of circulation causing extra costs in wellbore drilling. It is of the utmost importance to analyze the intensity of the instability of the wellbore depending on the direction and angle with which the weak bedding plane are perforated.
Medina, Leonardo Arias (Universidad de America, Bogota) | Lozano, Henry Andrey (Universidad de America, Bogota) | Mantilla, Hernan Dario (Ecopetrol) | Espinosa Mora, Carlos Alberto (Universidad de America, Bogota)
SUMMARY: After the success of the drilling campaigns in unconventional shale reservoir in the United States, Ecopetrol wanted to replicate their success in Colombia as well. During the past years a drilling campaign encountered several unique issues for shale plays in Colombia. With the advances in electrical logging, petrophysics, geomechanical and geochemical analyses allowed understanding the shale plays in a basin in Colombia.
Geomechanics has been useful in providing the required information for the design of optimal well trajectories for efficient development of unconventional reservoirs. Additionally, extensive tri-axial and total carbon organic (TOC) tests in shales have been included in the study to calibrate the mechanical properties and TOC obtained from the electrical logs. The concept of critically stressed fractures has been included in the analysis of this geomechanical model in order to know the conductivity of the natural fractures in shale plays.
The present study displays a methodology for the design of a mud weight window as well as a geochemical analysis for the sweet spot selection in the shale plays. The geomechanical model considers transversal vertical anisotropy (TIV) with the use of Stoneley wave from sonic scanner tool necessary for the determination of the anisotropic mechanical properties and in-situ principal stresses. The present study includes conclusions and recommendations for unconventional shale reservoirs in Colombia.
1 INTRODUCTIONOil companies have always wanted to drill wells in unconventional fields, but because of their complexity and limited technology in the time were an impediment.