First Massive Hydraulic Fracturing Treatment in Argentina

Abstract

Abstract In the last two decades, it was usual practice in the oil industry to carry out massive hydraulic fracturing works to stimulate wells with great-heighten layers of interest and/or low permeability sands. Argentina has had no opportunity so far to make a stimulation work of this type, mainly because of the absence of a layer meeting the principal characteristics needed to carry out a job of this size, considering the lack of equipment required by a service company to face the magnitude of the work in question. In the year 2000, Pan American ENERGY, a BP Amoco subsidiary, made exploratory works on a sand formation of interest that met the adequate characteristics to try and develop this kind of job. This paper shows how operator and service company designed this treatment in a team work and how this job was accomplished and came to be the largest stimulation treatment successfully done in Argentina to date. This kind of jobs can open a new way to handle tight gas zones in Argentina. Introduction Recently, different operator companies have discovered a series of new gas reservoirs at Grupo Cuyo level located in the Neuquen basin, exactly on Punta Rosada, Lajas and Molles formations awakening new expectations about this horizon. Lindero Atravesado field is located about 50 km NW from Neuquen City in the South of Argentina, see Figure 1. First wells were drilled on the sixties by Esso Co. They tested gas reservoirs at Sierras Blancas and Lotena sandstone formations. Two important developing stages took place along 1974 through 1986. The main objectives were the two latter formations while the Quintuco formation in the eastern block was the second objective. In April 2000 PAE LA xp-89 well was drilled at the south eastern side of the area located on the southern flank of the brachyanticline-type structure at 4216 Mts. final depth and drilling reached 115 Mts. (377 ft) at Los Molles formation. Grupo Cuyo total crossed depth was 1,237 Mts. (4,057 ft) of which 612 Mts. (2,007 ft) were at Punta Rosada formation; 510 Mts. (1,673 ft) at Lajas formation and 115 Mts. (377 ft) at Los Molles formation (partial). During well completion jobs, five levels were hydraulic stimulated between 3,200 Mts. (10,496 ft) and 3,991 Mts. (13,090 ft) corresponding to the Lajas and Punta Rosada formations where a 600,000 pounds massive frac treatment was performed (3823/65m - Lajas formation). Reservoir and Formation Characteristics A characteristic of the Lajas formation is the intercalation of psammitic and pelitic levels of variable thickness. The sandstone formations are medium to fine, medium and isolated coarse-grained and light gray colored. Occasionally, it intercalates scarce conglomeritic sandstone and conglomerate. It is a quartz composition (partly hyaline at the sequence base) and scarce reddish, greenish and light-gray lithics; in the lower part of the formation, the lithics are of tuffaceous porphyrites. Subangular grain shape predominates. It presents a tuffaceous-clayey white-colored matrix. Towards the base, the cement is siliceous and partly calcareous. It is presented with moderate consolidation. Visual porosity is low and low to regular of intergranular type in the conglomeritic fraction. The pelitic fraction shows claystone in a gray that goes from medium to light and a dark reddish brown at the top of the formation; the color is medium gray, medium greenish gray and medium brownish gray. It is an irregular sub-plane fracture. It shows fine and medium-sized carbonaceous and arenaceous inclusions. It also shows a moderate compaction towards the compact base.