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Friday, January 24, 2014
Longreach Oil & Gas reported on the drilling of its Koba-1 well on the Sidi Moktar license area in Morocco. The company said that it encountered a significant natural gas occurrence in the well and some difficulties besides.
The well was drilled to a total depth of 3,100 meters and had encountered a gross interval of approximately 45 meters of good quality Lower Liassic Jurassic gas charged reservoir commencing at 1,830 meters. This assessment has been made on the basis of visual examination of chip samples and side wall cores and from the amount of gas which entered the mud column while drilling and which was recorded by the gas chromatograph. The second drilling objective in the Triassic was not encountered in the section penetrated.
The Lower Liassic reservoir zone is normally over-pressured (4500 psi) as anticipated from nearby wells and the mud weight was adjusted to effectively handle that pressure. However, at 1,873 meters the well experienced a significant influx of salt water at an abnormally high pressure of 6000 psi. No other well in this area has encountered such high formation pressures at this depth. In order to control the well, which started flowing, the mud weight was steadily increased to 2.3SG before the well was stabilized enough to continue logging. Logging operations had to be halted a number of times in order to run back in the hole and recirculate in an attempt to stabilize the flow. Consequently the Lower Liassic reservoir zone was open to the heavy mud and abnormally high pressures for an extended period of time which resulted in damage to the well bore and significant invasion of the drilling mud into the Lower Liassic reservoir formation.
A normal series of logs were acquired and an MDT tool was deployed in an attempt to obtain reservoir formation pressures and collect gas samples. However, the logs and the MDT tool were not quantitatively effective due to the mud invasion and rugose nature of the wellbore. No gas samples were collected and only a limited number of pressures were obtained. Twenty side wall cores were collected confirming excellent reservoir quality.
As a result of the significant damage to the reservoir zone, Longreach is unable to reliably quantify the effective porosity, gas saturation or gas composition values for the Lower Liassic reservoir zone. At this time we do not believe that the high pressure water the Koba-1 well encountered is a gas water contact due to the significant differences in pressure between the gas and water-bearing zones. However, the Koba-1 well has proved that good quality, gas charged reservoir rocks are present thereby confirming the resource potential of the Longreach Sidi Moktar License. We continue to review the data and refine the timing of our follow-up drilling and testing program.
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