Gas Content Without Coring (GCWC) is a new service designed to measure the gas content of all strata drilled in an overbalanced mode using open hole techniques. The typical applications for this are:
- Initial exploration drilling – where the client wishes to avoid coring.
- Production hole drilling – where the client wishes to firm up knowledge of gas contents during the drilling of production holes.
- Where free gas is expected in such formations as porous sandstones where the gas would be lost on coring.
- Where the entire gas content of the stratigraphic sequence needs to be measured.
[youtube height=”360″ width=”640″]https://www.youtube.com/watch?v=iizGpjdNf4o[/youtube]
The system is not intended to replace gas content determination from core where this is targeting one or two well known coal seams or where core is required for other purposes. The system is however particularly useful in that it provides an absolute measurement of gas content through all the strata drilled.
The system can be installed on virtually any open hole rig that has a conventional mud handling system comprising mud tanks and a shaker. The additional equipment that is required comprises:
- Drilling rod head position measurement device.
- A dribble prevention valve at the water swivel.
- A pressure relief valve behind the bit.
- A rotary seal at the top of the hole. This may be fitted above the casing or over the BOP.
- A rate counter on the mud pump.
- A cyclonic separator placed between the outlet of the rotary seal with outlets for the gas flow meters and to the shaker.
- Gas flow and composition logging equipment.
- The ability to sample cuttings off the shaker.
These are simple additions to most drilling operations.