Geomechanical analysis to reduce well integrity issues in Eagle Ford drilling

Abstract

The oil and gas industry had an exponential increase in the development of the unconventional resources in particular in shale and tight oil reservoirs in the past few years. Oil prices climbed in the last decade reaching $150/bbl, but yet it has dropped down significantly before it started quickly to rise. From 2005-2013, the average price happened to be around $80 per barrel. This high oil price situation made the shale plays economical worldwide and attractive for investors and oil and gas companies to include into their portfolio. The Eagle Ford is considered the youngest shale play in the United States and holds a vast amount of hydrocarbon reserves. It extends from its outcrop belt in southwest Texas to northeast Texas, covering over 30 counties in Texas, more than one third of the State. The formation is considered one of the youngest shale plays and it became appealing after 2008 and it has been one of the most active areas in the United States in regards to drilling activities. The number of permits for drilling activities has been rising every year from the start of production in 2008, until 2014 when the oil prices crashed due to oversupply. According to Cunningham (2016) the breakeven price to the Eagle Ford is $56/bbl. Currently with the oil prices around $50/bbl more development is planned in the Eagle Ford; proper planning for the future development is essential. This includes addressing wellbore stability issues in the Eagle Ford that results in increasing the cost of the wells and the Non Productive Time (NPT). In this study, a geomechanical model was developed in order to investigate the proper mud weight window in order to prevent breakouts and fractures from happening in the wellbore and help prevent them in future drilling operations. A literature review to explain the general terms of the mechanical properties for rocks is done in the second chapter. These properties describe the stress state of the rock and are used in the calculation for the optimum mud weight. The third chapter explains the input properties and general forms to calculate these properties that are used in modeling the problem. The fourth chapter defines the equations that are used in MatLab application to show how we got the results. In the fifth chapter, the model results are presented and discussed. The conclusion and recommendations are stated in the sixth chapter.