Drilling and completion in tight reservoirs

OljedirektoratetPosted on

Substantial resources lie in “tight” reservoirs. Recovering these presents challenges, but new technology could make them profitable to produce.

Tight reservoirs have very low permeability or are inhomogeneous, with barriers to flow. Producing them calls for special well technology. That makes it important to adopt and further develop technological solutions which can contribute to efficient wells in tight reservoirs. New and improved methods as well as cost reductions will be important for the ability to produce from them.

READ MORE: Big potential in tight reservoirs

Example 1: Fracturing

Hydraulic fracturing (fracking) represents a relevant technology which has long been in use, and has been much utilised in tight reservoirs during recent years. It involves fracturing the reservoir rocks and keeping these fractures open by filling them with sand. The aim is to expose a larger area of the reservoir to the well. Oil and gas can then be more easily drained, increasing the production potential. To generate fractures and keep them open, water, sand and chemicals – primarily thickeners from the food industry – are pumped down the well.

One drawback with fracturing may be the difficulty of controlling the length and extent of the fracturing. Generating fractures vertically through rocks with varying properties can also present a challenge.

Example 2: Fishbones

An alternative technology with the same goal of increasing reservoir exposure area utilises small-diameter hollow “needles” drilled or jetted from the well liner. Projecting from the well into the formation, these laterals allow oil and gas to flow easily into the well. One advantage of this approach is that the length of the needles, and thereby of the “fracture”, will be known. The technology also makes it simpler to drill through strata of varying strengths.

One drawback could be the limited length of the needles and a smaller total reservoir exposure area than with fracturing.

Åsgard is the only field on the Norwegian continental shelf (NCS) to have tried out this Norwegian Fishbone technology, using it with the tight zones in Smørbukk Sør.

Åsgard is the only field on the Norwegian continental shelf (NCS) to have tried out this Norwegian Fishbone technology, using it with the tight zones in Smørbukk Sør.