Into my usual state of insomnia with a mix of high emotion after the last week.
But I'm not one to waste the wee small hours.
Been dog at a bone on the clay thingy given its importance in the initial stimulation sequence and have pretty much derisked it as much as possible to my level of knowledge as regards the company statement of NON-SWELLING CLAYS.
"the Company’s assessment is that the HRZ is a siliceous shale, most similar to the Haynesville and Marcellus, and will be highly amenable to fracture stimulation."
This will be exceptionally important when they frack the more consistent shale zones.
Its been a long time coming over the last year or so but its clear from various research done on Volcanic ash that when it avoids being exposed to the weathering vagaries on open terrain, that is when subjected to sub-ocean chemical alteration, that it gets the opportunity to convert to forms of clay that r then consequently amenable to diagenesis conversion (or sub strata changes due to heat and pressure) that result in the clay type called ILLITE.
It goes something like:
ocean deposition of volcanic ash > chemical alteration that results in smectites > sedimentary build up with volcanic ash incorporated at depth > burial depth/diagenesis alters smectite to illite.
It is a known geological fact that the HRZ was generated in a deep water ocean environment which was condusive for the above process to occur.
The core analysis at Ice 1 showed that the clays were indeed non-swelling in nature and I can only assume were therefore illite.
Illite is much more structurally stable than smectite as its ions within the clay lattice structure r tightly bound and r not nearly as subject to the volume alteration caused by reaction with water molecules which results in the swelling reaction associated with smectitic clays.
This item, if one has a basic understanding of chemical intereactions between atoms and molecules, explains via isotopic observations, how these diagenetic processes result in the clay alteration.
The alteration of volcanic ash in sedimentary environments can result in a variety of authigenic minerals, depending mainly on the composition of the parent material and the physical and chemical characteristics of the environment (e.g. pH and dissolved Si activity; Christidis, 1998; Ddani et al., 2005; Kiipli et al., 2007; Hints et al., 2008; Arslan et al., 2010; Huff, 2016).
In seawater, altered ashes are typically composed of authigenic illite/smectite and/or discrete illite, with minor amounts of feldspars, kaolinite, chloritic minerals, and primary volcanogenic phases. Illite and I-S clays in these ash beds are frequently interpreted as the result of illitization of smectite (Drits et al., 1996; Meunier et al., 2004). However, under hydrothermal conditions, pyroclastic material may be directly altered to mixed-layer illite-smectite clays, with predominantly smectite layers (De La Fuente et al., 2000).
During diagenesis, smectite will be altered to illite in the general reaction sequence smectite > random I/S > ordered I/S > illite. The ordering of I/S clays is correlated with the smectite layer content of the I/S minerals; the I/S structure will change from random (R0) to short range ordered (R1), and then to long-range ordered (R3), as I/S interstratified clays become more illitic (Bethke and Altaner, 1986a, 1986b; Ferrage et al., 2011; Dong, 2012).
Ashes in the PD section, deposited in relatively shallow water, contain mainly R2 and R3 I/S clays, with minor amounts of smectite, while their equivalent beds in the deeper XM section are more illitic, and much more ordered, containing only two types of R3 I/S clays (Fig. 4)
Again, not much detail is forthcoming in these linked 88E annmnts apart from the statement on NON-SWELLING CLAYS.
The reason for my concern was that the likes of Decker had maintained that the preffered chemical weathering process was that of volcanic ash to smectite. However it appears clear that smectites, if of the correct chemical ion/structure, will result in illites when exposed to diagenesis, and the % of illite is related to the time factor. In other words the longer the time the more conversion of smectite to illite.
Imo PB was always aware of this reactive potential of clay and hence his BELIEF in the HRZ as a high potential source rock.
(20min delay)