MIDHURST BORE

Taranaki Daily News, 26 September 1940, Page 6

MIDHURST BORE

CASING NOW NECESSARY SEAL1NG EFFORTS FAIL? REPORT BY COMPANY Efforts to overcome the trouble at the Midhirst oil bore by sealing off the soft sand strata which has delayed operations for some weeks have apparently failed, as the New Zealand Petroleum Company announced last night that the staff was preparing to set casing to shut off low pressure water and sands that have been impeding drilling progress. This is a stroke of bad luck for the drilling staff as each additional string of casing increases the natural difficulties of driving a well to the great depth contemplated. The soft sand was encountered some weeks ago a little short of the 2000 feet level and the effect was that the liquid mud pumped down the bore to prevent the sidea caving in and to carry away material cut out by the rotary drill began to leak out of the well. This meant not only that the bore round the bit was not being sealed by the mud but also that the hydrostatic pressure of the column of water which kept the well below the first string of casing from squeezing in had been lost. Drillers' Efforts. Every possible expedient was tried by the company to seal off the porous sand. The mud was thickened up and huge loads of papa were brought from Wanganui. Special chemical compounds were used and sugar beet waste was pumped in with the idea that wheri it absorbed a large quantity of moisture it would swell and provide something for the mud to cling to. As the strata was comparatively narrow it was hoped that these attempts would prove successful but the company's reports suggest that they have failed. The company has had bad luck at Midhirst, as the operations were earlier delayed when a reaming bit for widening the well to full width became jammed. This involved weeks of work and the removal of casing piecemeal. On the other hand, as if to compensate the company for its luck at Midhirst, everything has gone smoothly at Morere, the company's other well, on the east coast. That bore has now reached 4510 feet.