The paper presents the recent development of marginal oil and gas accumulations in the vicinity of the offshore Hidra field, by Total Austral operator and partners Deminex and Pan American Energy. Lying 12 km off the Coast of Tierra del Fuego in 35 m of water, the Hidra field was originally developed in 1989-1990 with conventional deviated wells drilled from two wellhead platforms, Hidra Centro and Hidra Norte. In 1996, three ER wells were drilled with a jack-up from these platforms to tap the Ara Sur and Hidra Sur accumulations. Although technical difficulties had to be overcome, the project was successfully completed. The first well (HNP-7) reached a horizontal departure of 6.2 km at 1700 m TVD representing more than twice the reach of previous conventional wells. This experience established the feasibility and cost effectiveness of ER wells, as a means of developing marginal oil deposits. Total and its partners decided to launch a second, more ambitious campaign in 1997, in which 9 ER wells were planned to be drilled, this time from the coastline. By May 1998, after a year of operations, 5 wells had been completed including the new American Continent record ER well, AS-3. Drilled late 1997 to a maximum departure of 7973m at a vertical depth of 1615 m, giving a HD/TVD ratio of 4.9, AS-3 was drilled and completed in 90 days. This technical achievement was the reward of intense engineering preparation, proactive attitude on the part of the project team and multidisciplinary teamwork and efficient risk management. The engineering preparatory studies are described, together with the rig mobilization, modifications and drilling operations highlights. A primary consideration of this project is protection of the unspoiled environment at the drilling site. The utter remoteness of the location has added a significant degree of difficulty to an already challenging task. An effort has been made with the mud logging company to improve the monitoring of hole condition, especially during the critical 12 1/4" phase, which reached 6700 m in length, at 80-85 inclination, using a device which measures in real time the total amount of cuttings flowing at the shale shakers. This data is combined with Pressure While Drilling data to further estimate hole cleaning efficiency and ECD. To overcome friction, the 9 5/8" casing of well AS-3 was run to 7720 m MD in flotation, requiring careful engineering and unconventional procedures and equipment. Landing into and drilling through the Springhill reservoir which is only 10 to 20 m thick and can exist locally in lenses, requires delicate geosteering techniques. This paper lists the main challenges that had to be overcome and the techniques employed. An economic comparison with other more conventional development schemes is outlined. The results achieved so far open the way to more ambitious targets which are presently under evaluation. P. 99

fax 01-972-952-9435. AbstractThis paper presents an innovative solution to monitor hole cleaning in Extended Reach Wells. It was successfully used while developing marginal oil and gas reserves offshore TIERRA DEL FUEGO (ARGENTINA) by TOTAL AUSTRAL operator and partners DEMINEX and PAN AMERICAN ENERGY.Keeping the hole clean in Extended Reach Wells is a key issue as cuttings accumulation will result in increased torque, pressure losses and will create a high risk of getting a stuck pipe.Cuttings Flow Meters (CFM) continually measure and record the flow of cuttings at the outlet of the shale shakers. This measurement allows an enhanced understanding of hole cleaning process and status, which in turn permits to optimize the main drilling parameters such as flow rate, rotation, circulation times, reaming time at connections and rate of penetration.It has been observed on those wells that the volume of cutting returns always fits with the actual volume of hole, over extended periods of time. By comparing on a permanent basis the volume of hole drilled with the volume of cuttings returned to surfiace, one can monitor the cuttings accumulation in the hole, one can thus better diagnose an increase in hole friction, adjust mud rheology parameters and circulating rate in order to minimize the surface and bottom hole circulating pressures while ensuring a good transport, all factors which are essentiat to further extend the drilling envelope.

A new gas logging system has been developed, field-tested and is now fully integrated in mud-logging units. In this system, the volume of mud put through degassing per time unit is a constant, whatever the actual drilling mud flowrate may be. Also, the greater amount of energy spent at the degasser increases extraction efficiency. Moreover, mud samples can be taken close to the bell nipple, without modifying the rig equipment, thus reducing surface gas losses. The gas show analysis is done through a double Flame Ionization Detector (FID) system, faster than most conventional systems. The sensitivity, even at low detection level, is remarkable. Field tests have been performed in the Paris Basin, where the GOR of the oil produced is very low. When conventional gas analysis devices do not detect anything, the new gas logging system enables a clear reservoir identification with good correlations with wireline logs. Another main feature of the system, also demonstrated by field tests performed in the North sea, is its ability to determine the compositional ratios of the light end components of reservoir fluids. This was verified by correlations with analyses of the associated gas produced with oil. The quality of the measurements performed by the new gas logging system will probably reinforce the reliability of mud-logging formation evaluation techniques.