There is an ever-present and ongoing need to better define, characterise and quantify exploration opportunities and producing reservoirs.
That’s why, for more than 15 years, HOT has been successfully integrating all of our clients’ engineering, wireline, seismic and rock-based data – including cuttings – in clastic, carbonate and volcanoclastic reservoirs. As core is relatively rare and cuttings are ubiquitous, HOT uses a semi-quantitative, microscopic technique called MACC (Microscopic Analysis of Core and Cuttings), also known as Drill Cuttings Analysis, to describe rock and pore characteristics and classify the drilled section into permeability classes.
“Drill cuttings provide a continuous, independent
and relatively inexpensive data source.”
Senior Reservoir Geologist, HOT
The ideal data set includes enough representative conventional core data for us to directly derive our geological model. In conjunction, wireline, seismic, and engineering data are used to develop and constrain our petrophysical, geophysical, and dynamic reservoir models.
However, for many reasons geological data sets may be somewhat lacking. That’s when uncertainty can creep into static and ultimately into dynamic models. To help manage this uncertainty we can substitute in drill cuttings.
From stored and perhaps forgotten drill cuttings lies a potential bonanza of data. Using MACC (Microscopic Analysis of Core and Cuttings), a technique described as ‘a visual method of semi-quantitatively describing rock and pore characteristics from either core or cuttings using a stereo, reflected-light, binocular microscope’ key characteristics such as lithology, grain size, sorting, framework components and cement types can be determined. By carefully observing these and other rock properties a relatively rich and importantly continuous data set can be generated and used for the interpretation of porosity and permeability, the identification of correlative surfaces, the interpretation of depositional environments and to develop geological models.
Our permeability estimates assign the sample to a permeability class or rock type that corresponds with an ambient value range and a geomean in millidarcies (Fig. 1).
Published data shows a strong correlation with production and test derived kh (Fig. 2).
A comparison of microscopically determined estimates of permeability (MACC) to those derived from drill stem test (DST) and routine core analysis (RCA) data
has shown that MACC is a valid and alternative means of accurately estimating permeability (Fig. 3).
MACC allows you to unlock your understanding away from core control as drill cuttings contain a wealth of critical information. You can verify your petrophysics, augment core-based porosity-permeability data sets and reduce uncertainty on your geological models. Additionally, the following characteristics can be determined:
Hard-grounds (exposure surfaces), bioturbation and rare coarse grains interpreted as being deposited in a paralic setting
Inter and intra granular and vug porosity in dolomite
Changes in grainsize, framework content and sorting differentiate depositional environments: e.g. floodplain and fluvial channel
Clastic and carbonate with visible connected marco porosity
Presence of open natural fractures indicated by growth of quartz crystals
Clastic and carbonate with negligible visible porosity
Geology and Geophysics
HOT Engineering GmbH Tel: +43 3842 43 0 53-0 Fax +43 3842 43 0 53-1 firstname.lastname@example.org