Positive Outcomes in the M1 Sandstone in a Mature, Low Structure Play – Tarapoa West Area, Oriente Basin, Ecuador

Abstract

Abstract

Oil was first discovered in the Tarapoa Block area in the Oriente Basin of Ecuador in the 1970's. After 40 years of exploration and development of the main productive reservoir of M1 sandstones, more than 300 mmbbls of recoverable reserves of medium gravity oil have been discovered.

The Tarapoa area is located in the eastern, westwardly dipping slope of the Oriente Foreland Basin. The M1 sands were derived from the eastern Guyana Shield area and deposited in a northwesterly trending series of estuaries as sandstones of primarily tidal/fluvial origin. Apart from the prominent northerly trending Fanny Fault, the area is characterized by low relief structures. The Fanny 1 well, drilled in 1972, was the first well in the large Fanny-Dorine oilfield. Not until the mid 1990's was the true potential of the area known, when seismic mapping showed the Fanny-Dorine field to be a stratigraphically trapped field with large scale, northwesterly trending shale barriers acting as the updip trapping feature to the M1 oil. The shale barriers can be clearly seen on 2D and 3D seismic data. The Fanny Fault which bounds the field on the west has always been considered as the main source of oil, and although other smaller accumulations of oil at Alice and Mahogany have been discovered downdip to the west of the fault, the western area was not considered to have significant potential since there were no large scale structural trends present.

In 2011, under new Ecuador Service Contracts, Andes Petroleum Ecuador was granted a block extension to cover a large area to the west of the Fanny Fault. Interpretation of the minor number of 2D seismic lines in the area recognized that the shale barriers extended into the Tarapoa West area. The presence of this key element to trapping oil, motivated the company to acquire 364 km2 of 3D seismic which allowed mapping of the shale barriers in an area in which only low relief structural closures occur.

The interpretation of the 3D seismic clearly shows the location and trends of the shale barriers which are key to trapping M1 oil in the area. The identification of the traps motivated Andes to drill several wells downdip from the shale barriers resulting in five new discoveries, four of which are directly associated with the stratigraphic trap and one which is a conventional structural trap.

These new wells have discovered significant new reserves and the developing fields are contributing over 10,000 bopd to the block production, a very important contribution to the company's production profile.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016