The Ishpingo-4 and Ishpingo-3 wells were drilled by Petroecuador - Ecuador's state-owned company - in the ITT (Ishpingo-Tiputini-Tambococha) field. This field is located in the Yasuní National Park in the Ecuadorian Amazon region, which was declared a World Biosphere Reserve by UNESCO in 1989. The Ishpingo wells were drilled primarily to delineate oil reserves, and the project was managed by Petroecuador and PETROBRAS ENERGIA S.A. (PE)professionals. PE contributed recent experience gained from drilling two appraisal wells, Apaika 1x and Obe 1x, across the lease line. These wells were drilled and tested within the same natural life reserve area with similar heliborne equipment, materials and personnel. To operate in this highly sensitive area, PE and Petroecuador developed a specific Environmental Management Program (EMP) that actively involved environmental authorities and representatives from native communities. The EMP was prepared using the PE Integrated HSE Management System certified by ISO14001 and OHSAS 18001. To assess the results, audits were jointly conducted by the Ecuadorian government, the native communities and the company. In 1992, two vertical wells - Ishpingo-1 and Ishpingo-2 - were drilled in the Ishpingo field. The additional appraisal wells were planned with extended reach trajectories from existing well locations to minimize environmental impact. The logistics, drilling and testing of the two high-angle wells were operationally successful, and the geological target was reached to confirm hydrocarbon occurrence and reserve size. Ishpingo-3 set records in Ecuador as the steepest dip well drilled in a 16-in. section and the steepest dip well out of all high-angle wells drilled in that country. The high-viscosity crude oil - 12° API - as well as the high-deviation angle of the wells prevented the use of conventional testing techniques. Therefore, special methods, together with state-of-the-art directional equipment, were employed to determine both deliverability and reservoir boundaries. The effective application of these technologies, with optimum allocation of there sources and good terrestrial-fluvial-aerial logistics, resulted in a highly successful operation overall. Introduction The ITT (Ishpingo-Tiputini-Tambococha) blocks held by Petroecuador and Block31 held by PE are located in the Yasun National Park (YNP) in the EcuadorianAmazon region. This park was created by the Ecuadorian State in 1979 and wasdeclared a World Biosphere Reserve by UNESCO in 1989. YNP is the Ecuadorianprotected area exhibiting the highest degree of biodiversity, includingamphibians, reptiles, mammals, fish and invertebrates. In addition, the numberof plant species in the YNP makes it Ecuador's second most important regionwith regard to flora diversity per acre. Because of its large spatial area (Fig. 1), the YNP can host healthyand stable stocks of any species over time (1999 YNP Strategic ManagementPlan). Most of the area covered by the blocks within the park consists ofpermanently or temporarily flooded forests. Vegetation consists of primaryforest with isolated human settlements. The park temperature ranges from 24° to26°C with 77% to 88% humidity, and precipitation exceeds 12,000 mm/yr. The YNP is inhabited by Quichua and Huaorani peoples. The Huaorani make up atribal community whose origins or historical references are unknown. The Kawimeno settlement dates to 1982 when the Taparon Anameni community, later known as Garzacocha and currently as Kawimeno, was founded with the help of the Capuchinos Mission. This is the only community near the project, located on thebanks of the Yasun River, which runs SW of the confluence with the Pindoyacu River. In 1992, two vertical exploration wells - Ishpingo-1 and Ishpingo-2 - were drilled by Petroecuador to 6190 ft (1887 m) and 5980 ft (1823 m), respectively. Oil was found in the Basal Tena, U and M formations. The fields contain heavy crude oil (12° to 14° API), and the wells are temporarily abandoned.