Production Performance of Radial Jet Drilled Laterals in Tight Gas Reservoirs in the Netherlands

Abstract

In the Netherlands, a significant number (25+) of small tight natural gas fields are stranded. They are classified, according to the PRMS definition, as ‘contingent resources’. The combination of low GIIP and low permeability currently do not allow these fields to be developed economically without stimulation, which is usually required to produce tight gas reservoirs. The recent change in legislation on hydraulic fracturing increases the need for a more cost effective and politically accepted alternative. Since natural gas has played, and will continue to play an important role in the energy security of the Netherlands, alternative methods are considered to extract these stranded resources. Radial jet drilling could be such an alternative method to develop these reservoirs in a cost effective, environmental friendly and socially acceptable manner. In this report, a numerical reservoir simulator is used to compare the production performance of a synthetic low permeable homogeneous reservoir based on three development options: a conventional vertical well, a vertical well stimulation through radial jet drilling and one case where the vertical well is stimulated through hydraulic fracturing. The static and dynamic models are based on typical tight gas reservoir properties as found in the Netherlands. The objectives are: to determine the operational scope / boundary conditions for the application potential of radial jet drilling, to identify the reservoir- and well variables that control the effectiveness and production performance, and to evaluate the economics. The comparison of the development option includes a sensitivity and uncertainty analysis of the well and reservoir performance and the impact it has on the economic viability. The simulations demonstrate that the laterals appear to be most effective in low permeable (~0.1 mD) reservoirs, reservoirs with near-well bore formation damage, with lower initial water saturation's, depleted reservoirs and thin reservoirs. The laterals appear less effective in more permeable reservoirs and reservoirs with high horizontal-to-vertical anisotropy. The application of small diameter laterals generally results in a recovery improvement factor of 2-3.5 compared to a vertical well. The initial gas production improves with a factor 4-7. The small diameter laterals become effective for reservoirs with permeabilities lower than 10 mD. In reservoirs with a permeability lower than 0.1 mD the application results in a recovery factor improvement of at least 2. The lateral length is the well design parameter that has the most profound impact on the recovery factor. The economics demonstrate that the onshore application of radial jet drilling as a stimulation method is economically feasible and robust whereas a vertical well is economically very marginal. The offshore application of radial jet drilling is only feasible for stranded volumes $>$ 1 BCM in combination with a re-entry scenario.