The goal of XRF Solutions is to use X-ray fluorescence (XRF) technology to provide chemical logs in vertical and horizontal wells. These logs help to in increase hydrocarbon production while reducing exploration and completion costs. XRF analyses are a rapid and relatively inexpensive way to gather large quantities of information at low cost per sample. Bulk rock chemistry is gathered in terms of both major elements and trace elements. Algorithms are applied to the data to provide geologic interpretations and rock property information for the client. Chemical analysis on drill cuttings allows for horizontal wells to be logged without the need for any tools down hole or impedance on drilling operations.
Figure A displays the mineralogical breakdown for the Glauconitic Member in a horizontal well. The minerals calculated through normative mineral calculations are Mg-dolomite, Fe-dolomite (ankerite), calcite, quartz, illite/smectite, kaolinite, and pyrite. Presence and amount of each mineral vary depending on the vertical stratigraphy. Mineralogy has a significant impact on bit wear, hydraulic fracturing and hydrocarbon production in the Glauconitic. It is very difficult to identify quantifiable differences between the upper and lower Glauconitic visually from geologist descriptions of the rocks. Based on background work conducted on two vertical pilot holes in the area it appears as though there is little or no Mg in the upper Glauconitic, while the middle Glauconitic has detectable Mg and is also easier to drill through. XRD work has confirmed that Mg is present in dolomite rather than a clay mineral.
Figure A. Mineralogy from Drill Cuttings Analysis in the Glauconitic Member.
The reservoir quality graph (Figure B) combines the key factors which are used to assess the overall reservoir quality. Major rock forming minerals provide an overall lithology. In many conventional sandstones the carbonate content is present entirely as cement. The relationship between quartz and Zr can also be used to estimate quartz cementation or chert content within a rock. Increased cement content will generally decrease rock porosity and therefore hydrocarbon production. In addition, drilling zones with higher quartz cement or chert content will tend to wear down the bit at a faster rate resulting in more bit trips. Rock mechanics can help to assess areas in which it may be difficult to induce fractures and also define potential fracture barriers. All these factors allow for the selection of a target interval which has the highest potential for success and the ability to stay within those itervals.
Figure B. Reservoir Quality Factors from Drill Cuttings Analysis in the Glauconitic Member.
Variations in chemical composition along a well can be used to position well within a detailed stratigraphic context. Figure C shows a well trajectory in the Glauconitic Member as it encounters different stratigraphic units. Within each formation there are distinguishable geochemical markers which can be traced from one well to the next for landing horizontal wells, geo-steering, reservoir modeling, and reservoir evaluation.
Figure C. Cross Section of Well Trajectory and Stratigraphic Units in the Glauconitic Member.