Hydrocarbon prospectivity of the miocene-pliocene clastic reservoirs, Northern Taranaki basin, New Zealand: integration of petrographic and geophysical studies

Abstract

In this study, it is aimed to characterize the Early pliocene sandstone (EP-SD) and the Late Miocene-Early Pliocene Mangaa sandstone reservoirs and the efficiency of their sealing cap rocks using the petrographical and petrophysical data of these sandstone zones in northern Taranaki basin, New Zealand. The prospective potential reservoirs were studied using impregnated thin sections, XRD data analysis, and well log data (self-potential, gamma-ray, sonic, density, neutron, shallow\deep resistivity and PEF) to characterize the reservoir zones, in addition to Mercury intrusion capillary pressure data (MICP) to check the efficiency of some potential seals. The EP-SD and the Mangaa sandstone units are typically poorly consolidated very fine sandstone to siltstone, with porosities averaging 25%. The sands are composed of quartz (38.3–57.4%), with common feldspars (9.9–15.2% plagioclase, and 2.7–6.3% K-feldspars) and up to 31.8% mica. In Albacore-1 well to the north of the Taranaki Basin, the Mangaa formation includes three separate for each of the EP-SD zones (EP-SD1, EP-SD2, and EP-SD3), and the Mangaa sequence (Mangaa-0, Mangaa-1, and Mangaa-2). The thin section studies indicate that, the studied samples are grouped into greywackes, arenites and siltstone microfacies with much lithic fragments and feldspars, sometimes with glauconite pellets. From the XRD data, it is achieved that the mineral composition is dominated by quartz, mica/illite, feldspars, and chlorite. The petrophysical investigation revealed absence of pay zones in the EP-SD zones, and presence of thin pay zone with net thickness 5.79 m and hydrocarbon saturation of about 25.6%. The effective porosities vary between 23.6 and 27.7%, while the shale volume lies between 12.3 and 16.9%. Although the shale content is relatively low, the relatively high API (50–112 API of average 75 API) is contributed by the relatively high K-feldspar content and intercalations with thin siltstone and muddy siltstone beds. Sealing units include the intra-formational seals within the Mangaa sequence, mudstones and fine grained units overlying the Mangaa and further intra-formational mudstones, within the shallower EP-SD units. The efficiency of these seals indicates the capability to trap 16.4–40.6 m gas or 17.4–43.0 m oil which is relatively low in correlation with their efficiency in the central parts of the Taranaki Basin Overlying the primary seals, mudstones of the Giant Foresets Formation provide additional regional seal.

Lithofacies Controls on Hydrocarbon Generation Potentiality of the Syn-Rift Late Cretaceous Rakopi Deltaic Facies in the North-Eastern Offshore Part of Taranaki Basin, New Zealand

“…The evolution of the Taranaki Basin coincides with late Cretaceous syn-rift extensional faulting related to the break-up of eastern Gondwana coupled with the formation of faultbounded graben and half-graben structures (Figure 3) [15,16,[36][37][38][39][40][41][42][43]. The Taranaki Basin constitutes two main structural provinces: the Eastern Mobile Belt (Taranaki Graben) and the Western Stable Platform.…”

“…Minerals 2023, 13, x FOR PEER REVIEW 3 of 22 of fault-bounded graben and half-graben structures (Figure 3) [15,16,[36][37][38][39][40][41][42][43]. The Taranaki Basin constitutes two main structural provinces: the Eastern Mobile Belt (Taranaki Graben) and the Western Stable Platform.…”

3D Static Reservoir Modeling of the Bahariya Reservoirs in parts of the Shushan Basin, North Western Desert, Egypt

“…Different methods were applied simultaneously to determine the lithology including the Density-Neutron, and the M-N lithology identification cross-plots which were recommended by many authors [24]. Estimating the M and N values are based on the apparent matrix density (Δma) and the apparent transit time of rock matrix (Δtma) as follows.…”