Reservoir Formation Damage Assessment in the Chicontepec siliciclastic oil-bearing reservoirs, Mexico

The Chicontepec basin contains about the 40% Mexico's reserves and is today the most important petroleum development project of the country. Since 2007, PEMEX started the Chicontepec's ambitious exploitation program which has the objective to compensate the country's oil production due to the natural depletion of the southern main oilfields. To date, this effort has resulted into the increment of about 30% oil production output. However, the expectation around this geologically-complex basin is still very high.

General characteristics of Chicontepec reservoirs, which are associated to a turbiditic origin, are low porosity/permeability ratios, texturally immature, and highly heterogeneous. These challenging characteristics make this reservoir often to be referred as an unconventional petroleum resource.

Hydraulic fracturing is commonly applied to these reservoirs in order to produce oil at commercial rates. However, oil production experiences a high decline rate, suggesting that formation damage is induced during drilling and fracturing. However, it is still unclear what reactions occur between stimulation fluids (e.g. gels, emulsions, foams) and reservoir minerals (both detritic clay and authigenic calcite cement).

Furthermore, knowing what the implications of employing incompatible fluids is yet an area of opportunity to be exploited by PEMEX specialists. In order to improve hydrocarbon recovery the most suitable stimulation technique for these reservoirs is required. Enhancing oil recovery would probably be the key to make this unconventional resource commercially viable.

A detailed characterisation of the petrophysical properties of the reservoir rocks followed by a series of laboratory tests will be performed in this project. From which, the most suitable substance(s) to be used as stimulation fluid will be identified.

The broad activities planned to be completed in this project are:

• Characterise reservoir rock, in terms of its pore geometry, mineralogical content and petrophysical character. This will help in recognizing the most representative rock types in the reservoir.
• Perform a series of flow experiments to find out the most suitable material (s) for enhancing hydrocarbon recovery. This includes the use of a range of fluids and rock types within the reservoir.

The ultimate aims of this project are:

• Provide to PEMEX specialist with the necessary evidence and tools to select the most appropriate fluid for stimulation purposes.
• Enhance stimulation practices in unconventional oil-bearing resources as of Chicontepec.
• Improve the ultimate hydrocarbon recovery, in order to make this type of reservoirs economically attractive.