Hydraulic Fracturing of Miocene and Oligocene Sandstones in the Taranaki Basin, New Zealand

Abstract

The Taranaki district of New Zealand, located in the southwest corner of the North Island, is the center of the country's emerging oil and gas industry. Over the last five years, an active campaign of propped hydraulic fracture stimulation has been performed in the early Miocene and Oligocene sandstones, located towards the south of the Taranaki sedimentary basin. Although hydraulic fracture stimulation is relatively rare in New Zealand, it has shown itself to be highly effective. This is due, in part, to the application of sound scientific and engineering principals, rather than the stochastic approach that is often applied when fracturing. The formations themselves are highly complex and consequently the techniques used for fracturing are at the cutting edge of today's fracturing technology. The results of the programme have significantly benefited from this methodical and progressive approach. This paper deals with the various aspects of fracturing into these formations and the lessons learned, including the equipment and methods used. It also details how the methods have evolved and allowed treatments to increase in both size and effectiveness, using numerous case histories. These detail what can be achieved in an area that is generally unfamiliar with the processes involved, when an existing technology is systematically applied. Introduction The Taranaki Basin1 Figure 1 shows the Taranaki basin, located to the west of the North Island of New Zealand, which comprises an area of approximately 100,000 km2 (62,100 sq miles). Although most of the producing fields are located onshore, the majority of the basin is offshore. The basin contains oil, gas and condensate reservoirs. A stratigraphic column for the basin is given in Figure 10 (see Appendix 1). The geology consists of Cretaceous to Quaternary sandstones up to 9 km (5.6 miles) thick. The basin morphology is composite as a result of several significant episodes of tectonic activity. The main source formations tend to be Cretaceous coaly sediments and early Cenozoic terrestrial and marine sediments. Reservoir formations are late Cretaceous to Eocene terrestrial-paralic-nearshore sandstones, late Cretaceous to Eocene coal measures, Eocene turbidites, fractured Oligocene limestone, Miocene volcaniclastics, Miocene turbidites and Pliocene prograding sands. The Basin is bounded by a major fault to the east, as illustrated in Figure 1 (the Taranaki Fault).

Contemporary tectonic stress pattern of the Taranaki Basin, New Zealand

“…Hence, localized deviation of stress due to small-scale stress sources can initiate complex and ineffective hydraulic fracture stimulations [Maxwell et al, 2009;Rajabi et al, 2016b]. This issue is particularly important for the Taranaki Basin where hydraulic fracturing stimulation is implemented to extract oil from reservoir rocks in some fields [Green et al, 2006].…”

Restimulation of Unconventional Reservoirs: When Are Refracs Beneficial?

“…New Zealand 101121 Green et al (2006) Swift Energy and BJ Services Hydraulic fracture stimulation and restimulation of Kauri and Tariki sands can be successful and economically achievable. Wells with little or no prefracture production will generally have little or no post-fracture production-good wells make good fracture candidates.…”