With the world’s fifth-largest estimated shale gas reserves, there is great potential for Saudi Arabia to replicate North America’s unconventional growth. Saudi Aramco’s unconventional program became operational in 2013 and the company has been working with major service companies, including Halliburton and Schlumberger, to develop the reserves.
The primary driver is the country’s pressing need to find new supplies of gas to replace the domestically produced crude oil used to generate most of its electric needs, demand that can reach as high as 900,000 B/D in summer. Another major aim is to use unconventional gas to bolster the country’s growing petrochemical industry.
Ali Almomen, an unconventional gas production engineer at Saudi Aramco, said the company has completed the exploration and appraisal phases of its derisking strategy and is in the middle of various pilot stages. He provided an overview of the company’s progress at the recent SPE Annual Technical Conference and Exhibition in Houston. “We are trying to fine-tune the technology, trying to reduce the cost, and improve the [estimated ultimate recoveries] further,” he said.
To accelerate the effort, the national oil company has so far committed at least USD 10 billion to its unconventional exploration program and is actively recruiting experienced unconventional experts from North America to join its ranks.
The company’s unconventional ambitions are focused on three different areas in Saudi Arabia. The first is located in the northern part of the country. The target formation is called the Qusaibia Hot Shale and is found at a depth between 6,000 ft to 8,000 ft. The shale is considered to be relatively shallow and is the source rock for conventional gas fields in the area. The gas produced from this area will support a major mining project still under construction and a new power plant.
The other two plays are in the eastern province and located along the periphery of the Ghawar oil field, the largest conventional oil field in the world. These two areas will benefit from their proximity to existing infrastructure and the large amount of geological data already collected from the development of Ghawar.
The play located to the south of Ghawar is a deep tight sandstone formation where five appraisal gas wells have been drilled so far. Sitting just east of Ghawar is the third play where Saudi Aramco is targeting a tight carbonate formation called the Tuwaiq Mountain—the source rock for the giant oil field. The company believes this field is comparable in many respects to the Eagle Ford Shale in Texas. “Sometimes, it is better than the Eagle Ford in terms of the permeability and porosity,” Almomen said.
The Tuwaiq Mountain formation is split into two tiers. The upper tier has nearly double the total organic content of the Eagle Ford while the lower tier is about the same. A pilot well drilled in the Tuqaiq Mountain formation had an average 30-day initial production rate of 3 MMscf/D of gas and 1,800 B/D of oil.
In addition to core samples and openhole logs, sonic logging tools and diagnostic fracture injection testing are being used to make key determinations about each formation’s permeability, pore pressure, and in-situ stress state. Using this information, completion engineers are placing as many as 16 fracture stages along the laterals. They are placing the stages only in the areas that appear to have the best production characteristics and are avoiding areas with poor reservoir quality. Based on production logs, Almomen said this strategy has resulted in 95% of the perforation clusters contributing to production in some of the best cases.
The company’s plans include using microseismic surveys and chemical tracers to better characterize fracture networks and to determine how cluster stages are contributing to production. The company is also investigating technologies to overcome the challenges involved with hydraulic fracturing in the middle of the Arabian Desert. “We are experimenting with local sand and we’re doing some research on water management, testing, and trying to create a decent frac fluid using sewage water, seawater, and other fluids,” said Almomen.
He added that once the company reaches the development phase, it will continue work on driving down costs and adopt factory-mode drilling techniques pioneered by shale producers in the US and Canada.
