Lukoil Saudi Arabia Energy Limited(LUKSAR) started a Deep ‘Tight Gas’ exploration campaign in the Rub Al-Khali Empty Quarter in 2006 and nine wildcat exploration wells have been drilled and evaluated with one Appraisal well in its Field Fig. 1. These prospective deep gas discoveries in the Empty Quarter have occurred in relatively High Pressure/ High Temperature (HP/HT) horizons at depths between 15,000 and 20,000 feet, where the stress and temperature are extremely high in addition to low reservoir permeability. This has made the exploration activity more challenging.
Well test and clean up results from different completion strategy has not yield convincing results due to many factors. Some of these include: well placement, fluid selection, completions and frac designs. Nonetheless, the starting point in evaluating the success of well operations in the life cycle of a well remains selection of suitable drilling fluid of which its solids and filtrate particles are very friendly to the given reservoir (i.e minimum damage effect). Although the drainage radius of these wells may be several hundreds of feet, the effective permeability close to the wellbore may have a disproportionate effect on the well productivity.
This paper summarizes the challenges encountered in the use of water-base mud (WBM) and the subsequent mud filtrate effect on the reservoir permeability through different test analysis on core samples and logs interpretations. But most importantly the result raises the need for continual research and development in the area of formation damage prevention and avoidance in deep gas drilling of ultra-low permeability reservoirs.