7.2. Production stimulation methods (psm)

Inflow (production) stimulation methods are technologies that increase the fluid inflow to the bottom of the producing well. After the formation drilling-in, the bottom-hole zone usually loses its original pool—reservoir properties. The structure of the pore space is disturbed, the clogging of the pore channels occurs, there is the removal of mechanical impurities. When the well is used for a long period of time there will be a process of scaling in the bottom-hole zone due to the mixing of different in composition of formation and injected water; because of the bottom-hole pressure drop there is the changing of stress-strain state of the bottom-hole that leads to pool-reservoir properties deterioration. According to the hydrodynamic researches of the wells there can be defined the productivity factor, hydroconductivity factor, permeability factor, piezoconductivity factor, saturation factor. According to the sign of skin-effect there is determined the state of the bottom-hole and the efficiency of the technology, used for the given area of the reservoir.

Inflow (production) stimulation methods include: re-perforation, perforation of additional intervals of undrilled oil-saturated formations, bottom-hole hydrochloric acid treatment (BHHAT), bottom-hole mud acid treatment (BHMAT), thermal acid treatment (TAT), thermal-gas-chemical formation treatment (TGCFT), hydrosandblast perforation (HSBP), surface-active reagent bottom-hole treatment (SARBHT), electro-hydraulic and acoustical effect on the bottom-hole, bottom-hole cyclic steam soaking.

So, the goal of inflow (production) stimulation methods is to improve pool-reservoir properties of the bottom-hole and to increase the productivity of the individual wells.

7.3. Enhanced oil recovery methods (eorm)

According to the properties, the enhanced oil recovery methods can be divided into groups: the first group increases oil displacement coefficient by water; the second one increases the sweep efficiency, and the third group increases both previous factors, and ORF (oil recovery factor) in general.

In contrast to PS methods, EOR methods affect the development object or its part, thus it allows to involve in the development the remaining, bypassed oil that were not extracted by means of project water flooding system. Practice has shown that the implementation of enhanced oil recovery methods is more expensive than water flooding, so the effectiveness of their use depends on the cost of the produced oil.

Enhanced oil recovery methods include:

physical - chemical methods - the use of aqueous solutions: active sadmixtures (surface-active reagent (SAR), polymers, micellar solutions, alkalis, acids, modification or conformance control (CC);

hydrodynamic methods - cyclic flooding, change of filtration flow directions, high injection pressure creation, forced fluid withdrawal (FFW), combined non-stationary flooding;

gas methods – oil displacement by high pressure gas, water-alternated-gas injection;

thermal, thermic methods – oil displacement by heat-transfer agents (hot water, steam), in-situ combustion;

other methods - the well grid compaction, the transition from one development system development to another (spot, selective flooding, creation of block-closed system), hydraulic fracturing of formation (HF), location and operation of lateral and horizontal well bores; microbiological, wave, electromagnetic methods.

Enhanced oil recovery methods are based on the following changes in the physical characteristics and oil conditions in the reservoir:

- Reduction of interfacial tension on the boundary of oil- displacement agent;

- Decrease of the mobility ratio of the displaced and displacing fluids (by reducing oil viscosity or decrease of the mobility of the displacing agent);

- Redistribution of oil, water and gas in the reservoir with the aim of oil reserves consolidation of oil reserves.