OPERATIONS REPORT KUBE KABE MAGNETOTELLURIC SURVEY KUBE91 - PAPUA NEW GUINEA The Kube Kabe project was a magnetotelluric (MT) survey undertaken by Zephyr Geophysical Services, Inc. for Chevron Niugini Pty. Ltd. in PPL 100, Southern Highlands, Papua New Guinea. The survey commenced on 12 July 1991 and was completed on 4 August 1991. The principal objective of the survey was a more complete mapping of thickness of the Darai Limestone in the general vicinity of the Chevron Wara #l well along the Wara and Kube Kabe Ranges. Data was taken in a full suite of frequencies from 384 Hz. down to .001 to .002 Hz. The most important range was primarily from 3 Hz. to .05 Hz. and using Cascade Decimation in the low frequencies it was possible to concentrate large numbers of samples in this range. The camp was located near the center of the Gobe Gap, just below an abandoned rig site. The camp itself was a relatively primitive fly camp consisting of two large covered, three sided shelters. The camp was built expressly for the MT survey and furnished by Exploration PNG, Pty. Ltd. It was centrally located for access to the survey area, and approximately five minutes flight time from Kantobo airstrip, and ten minutes flight time from Pimaga airstrip. All of the equipment was flown from Port Moresby via Milne Bay charter flights to Kantobo, Pimaga, or Mendi airstrips, depending on the weather. The equipment was then slung via helicopter from the airstrip to the Gobe camp for operations. Fuel and supplies were flown from Mendi to Kantobo or Pimaga via fixed wing and then slung to camp. One Hughes 500D from Pacific Helicopters was used throughout the survey. A total of twenty stations were recorded, with stations located along three distinct profiles trending roughly N30E, perpendicular to prevailing structures. The lines were identified as Wara (W) on the west, Masaka (M) in the center, and Wasuma (S) on the east. One central helipad was cut at each picked location, and all equipment and personnel were flown to this spot. The instrument tent was set up near the central helipad, and the sites themselves were installed 200-600 meters on each side of the helipad and recorded as remote referenced pairs. In addition, a set of remote magnetic coils were installed at the Wara rigsite and beamed via telemetry as a third set of reference coils to aid in reducing local noise on the magnetics. Logistics prevented the telemetry from working at several locations, and where the telemetered coils were used, the results did not indicate great improvement. Time series data were recorded at every station. The beginning of the survey was marked by bad flying weather. The crew and a small amount of equipment were in camp and ready to begin operations on 12 July, but bad flying conditions for fixed wing aircraft at Kantobo and Pimaga as well as Chevron cargo priorities caused a delay in arrival of sufficient gear to begin the survey until 19 July. At this time the survey commenced with the Wara line. WARA (7/19-7/23) ____ The Wara line started approximately two kilometers SE of the Wara #l rigsite and was composed of eight stations spaced in pairs along a line approximately S30W. The weather on this line was generally good, with light rain showers daily, but good visibility and no lightning. Stations WOl-W04 were in reasonably gentle topography, and stations W05-W08 were in severe Karst sinkhole terrain, with very rugged local topography between stations. Signal levels were generally up while recording this line, and combined with careful site layout and long telluric lines (200 m.) data quality overall was excellent. This line shows some of the cleanest MT data ever collected in PNG. The four setups on the Wara line were recorded in four nights and the crew moved to the Wasuma line next. The stations at the Wara rig site were 400 m. west and south of the drillhole, in an attempt to get away from any effect the casing or vertical hole might have on data. The data was marginal after one night of recording, and a second day was spent there. Data quality by the second night was quite good, and after checking at Wasuma again for visibility at S13-S14, equipment was slung to camp and packing begun. There were a total of 237.5 hours of recording on the survey, with fifteen days of production and two weather days during actual data collection. Helicopter time averaged approximately four hours per day for the MT survey itself plus camp resupply, fuel slinging, moving cutting crew, site scouting, etc. A total of six laborers on the layout crew and 8-10 local laborers on the pad-cutting crew were utilized, with Exploration PNG providing two foremen previously experienced in Zephyr MT operations. At the conclusion of the survey, all equipment was slung to Kantobo and removed via fixed wing to Moro, where it was transferred to Port Moresby for storage. STATION DESCRIPTIONS KUBE KABE MT SURVEY - JULY,1991 All stations were recorded with saltwater/bentonite mixture to help alleviate contact problems associated with limestone outcrop and shallow jungle soil. All stations were in thick double and triple canopy jungle, requiring cut helipads for instuments and drop zones cut at some site locations. Many stations required the use of a 100 ft. long line for slung loads due to the height of the trees. WARA LINE _________ WOl/W02 ------- Centrally located helipad approx. 2 km. southwest of Wara rigsite. WOl 300 m. along line N. of helipad, in moderately steep terrain. N. pot downhill at 10 deg. and crosses gulley 30 m. from pot. W. pot uphill at 20 deg. - site W02 250 m. S. of helipad along line, moderate terrain, S. pot only 20 m. length due to steep cliff. N. pot 200 m. to compensate length. W03/W04 _______ W03 approx. 200m. SW. of river, 200m. N. of helipad. Site on relatively flat ground, no unusual topo changes. Site W04 located 300m. SW of helipad on mild N. facing slope. Telluric lines even in all directions. Good top layer of soil for pots. W05/W06 _______ W05 along transect 250m. n. of helipad, moderately steep sinkhole terrain. N. pot travels uphill from depression, S. pot uphill also, E. pot across slope and even, W. pot slight uphill. Heavy limestone outcrop. W06 installed on steep sidehill 200m. SW. of helipad, sinkholes lOOm. across and lOOm. deep all along hillside. Tellurics relatively even overall across averaged ground. W07/W08 _______ W07 200m. N. of helipad along transect. Steep sinkhole terrain, large (lOOm. by 200m.) sinkholes with steep sides. Much limestone outcrop. Tellurics run diagonally across slopes as much as possible to minimize effect of topography. W08 in similar terrain, 300m. SW of helipad. WARA RIGSITE - W21/W22 ----------------------- W21 400m. W. of rigsite casing, on levelled auxiliary pad. Tellurics run into surrounding slopes, relatively mild slope correction overall. W22 400m. S. of rigsite, on cleared auxiliary pad with no connection to rigsite pad. Tellurics run into surrounding hillside. S. pot down steep (25 deg.) slope, W. pot down steep slope also. N. and E. pots across slope.