Many "poor" gas prospects-particularly ultralow-permeability and porosity unconventional rocks such as tight sand-become economic success when hydraulic fractures are created in the pay zone. The fractures allow a single well bore to contact many thousands of square feet reservoirs. Using swellable packer technology has mechanically simplified fracture job. Using multiple packers ensures the entire zone is treated; or in other words, knowing where the fracture fluid goes once it exits the casing, and how each set of fractures is isolated from another is a key in a successful hydraulic fracture design. Lukoil Saudi Arabia started an exploration campaign in the Rub’Al-Khali Empty Quarter in 2006 targeting Non Associated Gas and nine wildcat exploration wells have been drilled and evaluated. It was found during the early stages of the exploration that the gas accumulations in LUKOIL Saudi Arabia exploration Area (Block-A), were typically trapped in tight to ultra-tight reservoirs (see Fig. 1). These gas discoveries in the Empty Quarter have occurred in High Pressure and High Temperature (HPHT) horizons at depths between 12,000 and 20,000 ft, where the stress and temperature are extremely high in addition to micro-Darcy levels of reservoir permeability. This has made the exploration activity more challenging. Figure 1 Location of Project Area in Rub Al-Khali Desert

An engineered fluid formulation was designed to provide a 114-pcf non-damaging drill-in fluid for the Unayzah A and B sandstone reservoirs. Employment of potassium formate high density brine and manganese tetra oxide weighting agent provided superior drilling properties that delivered reduced formation damage, improved thermal stability, and lower drilling costs.The use of acid-soluble manganese tetra oxide allowed engineers to increase the density of potassium formate drilling fluids and extend the density window above that offered by calcium carbonate. The reduced particle size (D50= 1 micron) and the spherical shape of the manganese tetra oxide reduced friction and drag. This improved control of equivalent circulating density (ECD) and plastic viscosity (PV) and significantly lowered rheological profiles. These optimal properties were maintained at temperatures exceeding 155°C.Laboratory testing confirmed high performance features such as: 1. Excellent hole cleaning characteristics 2. Thin filter cake with low lift-off pressures 3. Low differential sticking potential 4. Low treatment cost during drilling and re-use capability 5. Superior rheological performance compared to high solids content oil-based fluids 6. Improved drilling performance and hydraulic efficiency with the formate base system.The vertical well in the Unayzah A and B sandstone reservoirs was completed with zero hole problems. The potassium formate/manganese tetra oxide system provided superior performance and stability even with elevated bottomhole temperatures in the tight gas formation. This paper reviews the laboratory design and development as well as the field application of the high performance, brine-based drill-in fluid.

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.

In this paper, attempts have been made to describe the experiences of 1.5 months of Managed Pressure Drilling (MPD) operations conducted in hard rock Formation in Rub Al-Khali, Eastern province of Saudi Arabia.The implementation of this technology arose from the lessons learnt from previously drilled 2 exploratory wells that penetrated the tight gas sandstone Formations of Sarah and Qasim at a depth exceeding 17,000 ft, where the temperature and stress are extremely high at 350 o F and 1.0 psi/ft respectively. As a result of these conditions, it is necessary in all cases to perform hydraulic fracturing to define fluid characteristics and evaluate production potential.The extreme low porosity range of 2-10 % coupled with low permeability range of 0.01 -0.26 mD and high fracture gradient interval of 0.9 -1.0 psi/ft are the main challenges on these wells. Moreover, other challenges faced include drilling with high overbalance mud weight across the reservoir and high abbresivity of the formation rocks resulting in difficulty identifying potential gas bearing sands and slow drilling rate respectively.As a part of the referenced exploratory activity in the 3 rd quarter of 2008, LUKSAR was challenged to drill across the target reservoir with minimum formation damaged, balance mud weight and swift reaction in identifying suitable coring interval. Hence, in response to these challenges, an extensive study and well design/engineering were carried out in order to accommodate the utilization of Managed Pressure Drilling (MPD) across Sarah-Qasim sandstone Formation on wells LUK-08 and LUK-09. This paper summarizes the well operation and in particular lessons learned during the first field application of Managed Pressure Drilling (MPD) in LUKSAR Exploration Campaign that resulted in significant improvement in well deliverability compared to previously drilled wells in Sarah-Qasim structure.