Enhancing Drilling Operations in SHYB Oil Field by Relating Drilling Azimuth to Formation Geomechanics: A Field Wide Case Study

Abstract

Abstract The Shaybah oil field (SHYB) is located in the southeast area of Saudi Arabia and it's where Saudi Aramco drills the most complex multilateral wells and runs the most advanced intelligent well completions. The target reservoir is the "Shuaiba," which is an extensively drilled carbonate reservoir. Also, the geomechanics and overall stresses of the Shuaiba were characterized back in 2001 in a study, which concluded that the maximum horizontal stress orientation in SHYB appeared to be north - south and that the magnitude of this stress is only slightly greater than, or equal to, the minimum horizontal stress making up what is known as a normal faulting stress state (Geomechanics International)2. Consequently, due to the limited amount of data that was available back in 2001, the conclusions regarding stress orientation would need to be confirmed as additional data becomes available. And nowadays, after 14 years of development, a larger set of data has become available. Therefore, the purpose of this paper is to supplement the results of the previous geomechanical study performed in 2001 using recent drilling data from 100 wells drilled after the previous geomechanical study was conducted. In other words, this paper uses the findings of recent hole stability data from 100 wells to confirm the earlier suggested normal faulting stress state. And based on the findings of this analyses, there was no strong evidence to suggest that the hole becomes significantly more stable when drilling along the maximum horizontal stress direction (N-S) or conversely, becomes significantly less stable when drilling in any other direction, especially in the minimum horizontal stress direction (E-W). This finding confirms the normal faulting stress in SHYB and that hole stability does not vary greatly with drilling azimuth for this specific field. Most of the last 100 wells drilled in SHYB were drilled along the NE - SW directions of the field. And from 84 wells drilled along the NE - SW directions, only six wells experienced hole instability. Also, out of 11 wells drilled in the N or S direction, which is the maximum horizontal stress direction, no hole stability issues were recorded. Out of the seven wells drilled in the E or W direction, which is the minimum horizontal stress direction, only one well experienced hole instability. Therefore, the findings of the analysis show that there is no strong evidence to indicate that significant hole stability improvement is achieved by drilling in the maximum horizontal stress direction. In conclusion, this paper discusses the results of a field wide case study performed using the drilling data of the last 100 wells drilled in SHYB. The available data seems to confirm the normal faulting stress state that was earlier suggested for the SHYB field. With this confirmation of stress orientation, the expectations for hole stability are improved and this reflects positively on well planning and overall field development.