Reservoir minerals

P. Somasundaran. Surfactant loss control in chemical flooding spectroscopic and calorimetric study of adsorption and precipitation on reservoir minerals—annual report for the reporting period September 30, 1992 to September 30, 1993. US DOE Fossil Energy Rep DOE/BC/14884-5, Columbia Univ, 1994. 

With the dump command, we cause the program to discard the minerals present in the initial system before beginning the reaction path. In this way, we simulate the separation of the fluid from reservoir minerals as it flows into the wellbore. The precip = off command prevents the program from allowing minerals to precipitate as the fluid cools. In practice, samples are acidified immediately after they have been sampled and their pH determined. Preservation by this procedure helps to prevent solutes from precipitating, which would alter the fluid s composition before it is analyzed. 

In the simulations, a significant fraction (about 50% to 80%) of the alkali present in solution is consumed by reactions near the wellbore with the reservoir minerals (as shown in Reaction 30.6 for the NaOH flood), mostly by the production of analcime, paragonite, and dawsonite [NaAlC03(0H)2]. In the clastic reservoir considered, therefore, alkali floods might be expected to cause formation damage (mostly due to the precipitation of zeolites) and to be less effective at increasing oil mobility than in a reservoir where they do not react extensively with the formation. 

Adsorption or possible chemical reaction of the surfactant with reservoir minerals is also a limitation. In general, the cationic surfactants are of very limited value because of this factor. Nonionic surfactants are usually the best, particularly where significant clay deposits are present however, anionic surfactants are in some cases equally effective. 

PPGs are strength- and size-controlled ( am-cm), environment-friendly, and stable up to 110°C in the presence of almost aU reservoir minerals and formation water salinities. 

The point of zero charge of the reservoir minerals, their physical structure, the surfactant equivalent weight and structure, and the structure of the electrical double layer at the solid/solution interface appear to be major factors determining the mechanism of adsorption and potential surfactant losses in surfactant flooding. 

Aging effects. Diagenetic effects, which, apart from chemical processes (sorption, precipitation, occlnsion, incorporation in reservoir minerals and other geosorbents such as char, soot and ashes), involve enhanced mechanical consolidation of soil and sediment components by compaction, loss of water and mineral precipitations in the pore space, may induce a quite essential redaction of the reactivity of solid matrices (e.g. Lnthy et al., 1997). 

Somasundaran, P. Adsorption from Flooding Solutions in Porous Media A Study of Interactions of Surfactants and Polymers with Reservoir Minerals U.S. Department of Energy Bartlesville, OK, 1989 DOE/BC/10848-15 (DE98000733) Contract No. AC19-85BC10848. 

Therefore, reservoir minerals are expected to have a selective immobilization capacity for certain pollutants or trace elements. Mineral phases with special surface properties and amorphous materials may also be considered here (Table 9.8). Reservoir minerals may form in a wide range from high-tem-perature processes to temperatures of diagenesis. 

Techniques involving reservoir minerals are mainly applied on industrial process residues. Pbllmann (1994) has demonstrated two different ways to the formation of a sta-bilizate, where pollutants can be stored for a long period of time. In the first case, primary reservoir minerals, which exhibit no hydraulic reaction, act as widely inert filling substances for hydraulic formations within the landfill. In the second case, a new generation of minerals, which also can incorporate pollutants from the water phase, fills the pore space. By using such condensation processes, water permeability is reduced, and consequently also the dispersion of pollutants by convection. 

Tab. 9.8 Examples of inorganic reservoir minerals for hazardous elements occurring in various waste materials. (From Bambauer and Pollmann 1998.)...

TABLE VII. ELECTROPHORETIC MOBILITY OF TYPICAL RESERVOIR MINERALS VS. VARIOUS ALDALINE SOLUTIONS... 

New formations of "reservoir minerals" can incorporate potential pollutants in their internal structure. 

Fig. 10.11. Procedural steps for the formation of reservoir minerals from industrial mineral residues (Pollmann 1994)...

There are two additional types of chemical flooding systems that involve surfactants which are briefly mentioned here. One of these systems utilizes surfactant-polymer mixtures. One such study was presented by Osterloh et al. [72] which examined anionic PO/EO surfactant microemulsions containing polyethylene glycol additives adsorbed onto clay. The second type of chemical flood involves the use of sodium bicarbonate. The aim of the research was to demonstrate that the effectiveness of sodium bicarbonate in oil recovery could be enhanced with the addition of surfactant. The surfactant adsorption was conducted in batch studies using kaolinite and Berea sandstone [73]. It was determined that the presence of a low concentration of surfactant was effective in maintaining the alkalinity even after long exposures to reservoir minerals. Also, the presence of the sodium bicarbonate is capable of reducing surfactant adsorption. 

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