Increase oil production from mature reservoir near OWC

Ecuador has several mature subhydrostatic sandstone reservoirs that have a lateral water drive or are located close to the OWC. Over time, the water saturation increases and water breakthrough is common in high-permeability streaks, substantially increasing the water cut. Petroamazonas wanted to increase oil production and recoverable reserves from one such reservoir in the Lago Agrio field, without further augmenting the water cut. Conventional hydraulic fracturing was not deemed to be a viable option because of the close proximity of the oil and water zones. Acid treatments with diverter stages to selectively stimulate the oilsaturated intervals and relative permeability modifiers to limit water production had been tried in other similar reservoirs but had not proved reliable.

Fracture using fluid that limits water production

Hydraulic stimulation using FracCON water-conformance fracturing fluid was proposed as a solution. This linear gelled polymer fluid has been specifically developed for high-water-cut wells with recoverable reserves near the OWC or gas/water contact (GWC). It features a newgeneration relative permeability modifier (RPM) for mitigating water cut after fracture stimulation treatments. The fluid’s unique combination of low viscosity and excellent fluid leakoff control and proppant transport capacity limit the net pressure and the risk of fracture height growth—without compromising proppant placement. The result is fractures that stay in the pay zone; less fluid and proppant are required to achieve longer and more conductive fractures, leading to more oil and less water production.

Even if the hydraulic fracture breaks through the OWC or GWC, adsorption of the RPM onto the fracture faces reduces effective permeability to water and prevents it from flowing. The ionic nature of FracCON fluid enhances its adsorption characteristics and minimizes desorption during the production cycle, prolonging the effective life of the treatment.

Improve oil recovery significantly while reducing water cut

The first hydraulic fracturing campaign for Petroamazonas using FracCON fluid consisted of eight wells in the Hollin formation, which has a strong aquifer 5 to 20 ft away. The upper section of the formation produces oil while the lower section is water-saturated. After the treatment, average oil production increased threefold (adding more than 450 bbl per treated well per day), while the water cut decreased by 15%. Petroamazonas has since used this fracturing fluid successfully in different fields and formations. Over 40 wells have been treated, increasing production by more than 10,000 bbl/day. Providing a reliable means of selectively increasing oil production has a very positive impact on the economics and reserves recovery in marginal fields.