The main objective of the laboratory and field studies was to develop an efficient and flexible reservoir conformance control (RCC) technology through improvement of the standard silicate method with joint application of "liquid” polymer and nanoparticle (silica) suspension. Similarly, the important idea was to simplify the surface facilities and reduce cost of chemicals, treatment time, and human force. The laboratory studies focused on laser particle sizing, dissolution kinetics, colloid chemical, rheological, gelation kinetics and setting time, and flow properties of polymer and nanosilica containing silicate gel methods in porous media (sandstone). Based on the experimental findings, it was found that “liquid” polymers and “liquid” nanosilica readily and rapidly dissolve and mix in water, and the solutions are free of microgels and the mechanical entrapment was minimal even in low permeable sandstone cores. In addition, they decreased significantly the surface tension and interfacial tension. It was proved that such “liquid” additives provide unprecedented flexibility to the technology and the enhanced methods may be attained with labor and expenditure effective way. The main effect of polymer was to stabilize the silicate gel against syneresis (spontaneous fracturing) and formed a secondary network in gel and that fact provided more thermal stability of gel. The nanosilica beneficially influenced the gelation kinetics of polymer containing silicate solutions. The main effect could be traced back to advanced nucleation of gel formation. Additional positive effect of nanoparticles is that its presence in the reaction mixture makes more flexible the pH control in both the bulk phase and in porous media. The extra beneficial properties of “liquid” polymers and nanomaterials in all oilfield chemical applications may significantly contribute to improvement of standard technologies; meanwhile the surface facilities can be simplified, or completely eliminated (e.g. the “liquid” polymer and nanosilica can be directly injected to basics sodium silicate solution at wellhead). Earlier, the “liquid” polymer was successfully applied in water shutoff in Oman. Recently, a new field programs is running in Hungary using silicate/polymer solution with nanoparticle (silica) fillers. The paper details the “from laboratory to field” activities, and demonstrates the superiority of the novel concept. The successful field pilots, the join application “liquid” polymers, and nanosilica may open new vistas in reservoir conformance control.

The primary aim of the research project was to develop an efficient technology to control excessive water production in gas wells. As a novelty, water sensitive petroleum-based solutions were developed, which spontaneously form extremely high viscosity barrier under reservoir condition when contacting with water. The beneficial effects of induced phase inversion of metastable systems on restriction on water flow were already detailed in previous papers and later the technology was deemed matured and necessary to test under field conditions. Two phases and the still running field pilots were accomplished in one of the gas capped oil reservoirs of the largest stacked hydrocarbon field Algyö, Hungary. The target gas wells were operating in the gas cap over the oil layer depleted by double-sided water injection. Until now, six active wells were treated with the self-conforming microemulsions including two repeated cases.Analyzing the production history of wells, the detrimental (Ͼ50 m 3 /d, sometimes much higher than 100 m 3 /d) water production was the primary factor selecting the target wells to be treated. Usually, 40 -100 m 3 microemulsion was injected into the wells after drying the vicinity of wells by water-miscible organic solvent and N 2 injection. The post-injected inert gas also served to create deep penetration of the treating solution in the reservoir. The jobs were completed within 1-2 days, and after 2-3 weeks of shut-in period, the gas production was restarted. Evaluating the field results, it was concluded that the treatments prove a multifunctional mechanism. The water production in some wells dropped significantly (from 120 m 3 /d to 40 -30 m 3 /d in one well); meanwhile the gas production remained unchained. In one well, the water production remained unchained, however, the gas production tripled. Surprisingly, all treated wells, never producing liquid hydrocarbons in the earlier period, started to produce substantial amount of oil (oil cut between 10% and 75% oil in net fluid rate). These positive results can be attributed to three different reasons: effective barrier formation against water influx, reducing skin factor caused by formation damage, and opening new flow paths from entrapped oil bodies existing below the gas cap. Thus, the treatment technology was qualified as a Љmultifunctional well stimulationЉ in contrast to the original term of Љwater shutoffЉ method. Based on the encouraging field results the technology became one of the strategic projects of the company in the coming years until 2020.

The different water shutoff treatments based on in-situ gelation are attractive technologies; however, the field results often fall short of expectation. Reason of unsuccessful treatments might be that the flow resistance against water often develops not in the right time and reservoir space. Therefore, the primary aim of the research project was to develop such chemical systems, which will form the blocking phase triggered by mixing with water. As a novelty, water sensitive petroleum solutions and external microemulsions were developed, which are stable until they are diluted with water forming thus stable water external macroemulsions. Phase inversion of such metastable systems to stable ones in reservoir may radically restrict the water flow through their high viscosity and entrapment of the dispersed particles by the pores. The transformation and structure of phases were analyzed by photon correlation spectrometry, rheometry. The core studies confirmed that all metastable systems reduce the flow of water by 80-90% in water-saturated sandstone. Using chemical-free postflush the flow resistance remains substantial against water; meanwhile the permeability deterioration against gas is negligible.The petroleum microemulsions are in phase of pilot test in two gas wells in the largest Hungarian oil/gas reservoir (Algyő field) with the aim at restricting the substantial water production. The concept and the developed technology is similar to the earlier silicon microemulsion field test, which yielded 3 106 m3 incremental gas production in the same reservoir and measurable decrease in water production. The metastable systems may offer an excellent opportunity for water shutoff in matured gas fields and gas storage facilities. The unique properties of the techniques are that flow resistance may occur only in water saturated reservoir space and in case of technical failure; the flow barrier can be eliminated by oil and gas injection.

Water shutoff treatments need different approach and chemicals in gas and oil fields due to the inverse mobility ratio. Therefore, the primary aim of the research project was to develop special treating solution, which may form barrier phase against the flow of water by in-situ mixing of the treating fluid with formation water. As a novelty, water sensitive petroleumbased solutions were developed, which are stable until they are contacted with water. The induced phase inversion of such metastable systems restricts the water flow by 80-90% in sandstone cores through evolving extremely high viscosity in the mixing zones. Optimizing the composition of the treating fluid containing environmentally friendly chemicals the method was qualified as matured for field pilot tests.Evaluating the production history of possible alternatives, two gas producing wells were selected for the pilot. The wells are operating in different layers of the largest, stacked Hungarian oil and gas field. Prior to treatment, in both cases, the gas rate dropped significantly; meanwhile the water production rapidly increased to 120 and 150 BPD, respectively. The injection protocol started with partial reduction of water saturation in the nearby zone of wells by injection of water-miscible organic solvent driven deeply into the reservoir with N 2 . Afterwards, the petroleum bulk solution containing tenside and fatty acid ester in appropriate concentration was injected. Injecting 40-50 m 3 treating solution, nitrogen drive served again to reach deep penetration of treating solution. Monitoring the wellhead pressure it was clearly indicated when the induced phase inversion started to build-up resistance against the water flow. Applying short shut-in time, transient production period was observed, which was followed by gradually increasing gas production with water-free and reduced water influx. The preliminary data firmly proved that the unique water shutoff technology might open new vistas reservoir conformance control in gas fields.

The unconventional gas reservoirs usually have extremely low permeability, small average pore sizes, and often absolute water-wet surface character. As a result, the residual water saturation and the critical capillary pressure needed to mobilize water from natural porous systems might also be unexpectedly high. Therefore, a detailed laboratory studies have been carried out with the aim at determining the detrimental effects of pore structure, wettability, capillary and imbibition forces, and permeability in tight sand gas and BCGA reservoirs. Based on experimental results, it was proved that the water was a natural blocking phase. Namely, the water may cause serious formation damaging hard to cure when the reservoirs were ever contacted with water. Hence, the operators definitely face with difficulties when water-based fluids are used in drilling, well completion, fracturing, and production technologies. Consequently, the physico-chemical considerations suggest that application of water-free fluids is recommended in any phases of field operations. Similar difficulties are arising in respect to gas transport in tight media. Since the mass transport is usually diffusion, the driving force of gas production should be treated with weaponry of physico-chemical approach and thermodynamic calculations. The paper to be presented will also focus on critical PVT problems of fluids saturating the reservoir space. It will be shown that gas/liquid equilibrium of some fluids (e.g. water and heavy hydrocarbons) and supercritical phase equilibrium of light hydrocarbons, CO2 and H2S may have significant influence on rate and composition of gas production. Thus, new paradigms and theoretical approach are necessary in the future, and further fundamental and applied research seems to be indispensable to develop novel recovery technologies for gas recovery from unconventional gas reservoirs.