Reservoir Continuity

Chromatograms in a reservoir continuity study are compared in a star plot.

Chromatograms in a reservoir continuity study are compared in a star plot.

When wells unexpectedly begin to lose productivity, reservoir depressurization may be to blame.  While well injection can remedy this problem, it ceases to be a viable option if significant intra-reservoir obstructions exist. The presence of these obstructions can be determined by a continuity study.  First, gas chromatography is performed on samples from wells in need of assessment to ascertain the chemical “fingerprint” of each oil sample for comparison, measuring the individual components and charting them in a chromatogram. Each chromatogram consists of a series of paraffin peaks with other components plotted between the paraffins. If a difference of 10% or greater can be observed between the intra-paraffin peaks of any two samples, they are not in communication and likely come from separate compartments of the reservoir.  If oil samples from an entire reservoir cannot be obtained, it is also possible to use rock-extracts as stand-ins for an oil sample.