OIL EXPLORATION

Otago Daily Times, Issue 23691, 24 December 1938, Page 11

OIL EXPLORATION

PETROLEUM COMPANY'S SCHEME DRILLING OPERATIONS EARLY HOPES NOT REALISED (Per United Press Association) GISBORNE, Dec. 23. The officials of the New Zealand Petroleum Company in charge of the oil exploration scheme at Totangi have not had their early hopes realised in connection with the effort to restore the lost verticality of the hole. After the Christmas close-down drilling will proceed slowly dnd cautiously in a renewed effort to straighten the well, which is reported to have taken a deviation of between four and five degrees from the vertical. The deviation is a matter of great significance itself, but the company is anxious to overcome the early deflection in order to ensure that the test of the Totangi dome is complete. If the deflection should continue and become aggravated the value of the exploratory work undertaken will suffer. The difficulty now encountered is of a routine character. It is especially likely to occur in " deep-dip " geological structures where the strata take steep angles as in the Totangi .dome. The strata through which the drill is working is mainly hard sandstone, with occasional alternations of lighter rock, and the angle at which they lie acutely is opnosed to the direction of the drill. The tendency of the drill to move off the vertical line had been noted early in the process of sinking the well, but only recently did it assume proportions calling for special attention. The customary first remedy is to fill the hole with cement to the point where the deflection becomes noticeable, and after an interval to allow the cement to harden, to redrill that portion of the hole. In the first effort at cementing success was not achieved, however, and after the first few feet had been gained the drill slipped into its old channel and began to take out the cement, which was not fully set. A second endeavour to overcome the deflection is now proceeding, the bottom of the hole having been refilled with cement to about 2300 feet, and this filling will be left until Wednesday next, when drilling will be resumed with a small pilot bit. The enlargement of the hole to the maximum diameter will be undertaken later, when the success or non-success of this system is known. If necessary the hole will be deepened further and when a softer series of strata is encountered corrective measures will be applied with a fair prospect of success. Such operations are in the normal experience of oil well operations, and the officials are confident that they can take the well down to the desired geological horizons with a minimum of deviation from the verticalitv. The hard sandstone strata encountered at Totangi present a problem not novel but calling ,for the utmost care in its handling. The worst development that could happen would be the aggravation of the deflection to a degree which would prevent penetration ■of the structure known as the Totangi dome. If the drill were allowed to slip down the flanks of this structure it would finish up outside the area wherein lie the best prospects of oil production.