A group led by Petrodorado Energy Ltd., Calgary, will test a thick new sand-prone package at the Dorados-1X indicated discovery on the Talora block in Colombia’s Upper Magdalena Valley.
Dorados-1X reached a final depth of 7,282 ft, about 2,200 ft above the originally planned total depth. Petrodorado drilled 600 ft below the 6,685-ft depth reported on Sept. 25. Some 400 ft was similar to the sand-prone section previously reported. As the remaining 200 ft was considered to be in “economic basement” (possibly the Jurassic Giron formation), drilling was halted.
Participant Sintana Energy Inc., Plano, Tex., previously reported that the well had encountered an extensive interval of a new Cretaceous sandstone, Cenomanian in age and therefore younger than the original Tetuan and Caballos objectives. It is evident that these thick, quartz-rich Cenomanian sands, which appear to be thicker than the standard plays in the area and have superior petrophysical characteristics, define a new exploration play, Sintana Energy said.
The new sand-prone package measures in excess of 1,700 ft of gross sandstone section, the lowest segments of which may be Cretaceous Albian in age. The hydrocarbon-bearing characteristics of these sandstones remain the same as previously reported with 876 ft of excellent wet gas shows between 5,160 ft and 6,036 ft as defined by gas chromatography and mass spectroscopy and an estimated 316 ft of oil shows based on the mud logs between 5,720 ft and 6,036 ft.
Below 6,036 ft the well appears to be water wet based on a drop in shows and petrophysical analysis. This is taken to simply represent a normal water line for this particular structure or structural compartment, Sintana Energy said.
With a possible hydrocarbon column of more than 800 ft, the Dorados-1X discovery interval would be exceeded only that at Guando field 40 km southeast with an original gas and oil column of more than 2,100 ft.
Sintana Energy said, “The key conclusion thus far from drilling results of the Dorados-1X exploration well is the presence of a younger Cenomanian sand sequence that appears to represent a thicker and better quality reservoir than the typical Tetuan and Caballos found in this area of the Upper Magdalena basin.”
Sintana Energy’s fundamental technical strategy is to identify well-defined thrust anticlines in areas of mature and abundant source rock section--prospects such as Dorados--such that the only remaining geologic risk is reservoir quality. Seals are excellent.
The company’s exploration concept in the northern basin area is to discover new or overlooked fluvial and paralic sand systems within the Middle and Lower Cretaceous sections where exploration and deeper drilling have been largely absent.
The forward plan for Dorados-1X is to flow-test six Cenomanian sandstone intervals. Both fractures and matrix porosity reservoir mechanisms will be evaluated.
The testing program is being designed to adhere to strict efficiency guidelines in order to contain costs and ensure that each test interval will depend on the favorable flow characteristics of the preceding tests. Petrodorado will use a low-cost rig and anticipates that testing will commence by mid-November.
Doug Manner, Sintana Energy chief executive officer, said, “Given the dimensions of these multiple sand sections, and their mineral assemblages, our technical view is that they are likely to have considerable areal extent. Not surprisingly, the partnership’s testing and exploration efforts have shifted to these younger sands.
“In parallel with the evaluation of this discovery we will continue our hunt for the Tetuan shales and carbonates and Caballos sandstones in other wells, such as in the nearby Verdal-1 well (drilled in 2010).”
Sintana Energy has an undivided 30% private participation interest in the 58,570-acre Talora block. Talora is 60 km west of Bogota and adjacent to the region’s main oil and gas pipelines.