Development of Low Permeability Reservoir Utilizing Multi-stage Fracture Completion in the Minimum Stress Direction

Abstract

Abstract Saudi Aramco is developing several gas fields in the Eastern Province of Saudi Arabia by drilling horizontal wells in the Khuff and pre-Khuff tight carbonate and sandstone formations. To date, many wells have been drilled in the maximum horizontal stress direction with virtually no wellbore instability occurring during the drilling operation. When these wells are hydraulically fractured, the fracture grows along the wellbore in the direction of well azimuth. To avoid overlapping of two adjacent induced fractures and thereby communication between stages, only 2–3 multi-stage fracture treatments can be performed. Depending upon the length of wellbore-reservoir contact, reservoir development, and stress barriers, more than four fracture treatments can become redundant or even cause premature screen-out in proppant fracture treatments. Wells drilled in the direction of minimum horizontal stress are potentially more favorable from the perspective of reservoir development and optimal production. In such a situation, hydraulic fractures grow transverse to the wellbore axis allowing multiple fractures to be placed without the possibility of fracture overlapping. Consequently, few wells that have been drilled in the minimum horizontal stress direction encountered several drilling-related problems, such as stuck pipe, breakouts, and breakdowns. A comprehensive study was conducted to overcome the wellbore stability issues and investigate feasibility of drilling wells in the minimum horizontal stress direction. Correct mud weight (MW) prediction is one key factor during the drilling stage to keep the wellbore stable and deliver good borehole geometry to run multi-stage fracturing assembly without complication. Multiple transverse hydraulic fractures easily created in such wellbore geometry maximize reservoir contact area and increase productivity of the low quality tight reservoir. The key objectives of the study were to define a safe MW program for the horizontal section of the planned wells by conducting a wellbore stability study, and to determine a real-time strategy to mitigate and/or manage wellbore instability problems as they arise. The scope of work included root cause analysis of drilling events, development of Mechanical Earth Models (MEM) for offset wells, integrating sections of the mechanical earth model from the offset well to the planned well trajectory and a safe MW program for planned well.