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Confined phase envelope of gas-condensate systems in shale rocks

Nagy S., Siemek J.

Archives of Mining Sciences

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2014

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Vol. 59, no. 4

1005--1022

EN

Natural gas from shales (NGS) and from tight rocks are one of the most important fossil energy resource in this and next decade. Significant increase in gas consumption, in all world regions, will be marked in the energy sector. The exploration of unconventional natural gas & oil reservoirs has been discussed recently in many conferences. This paper describes the complex phenomena related to the impact of adsorption and capillary condensation of gas-condensate systems in nanopores. New two phase saturation model and new algorithm for search capillary condensation area is discussed. The algorithm is based on the Modified Tangent Plane Criterion for Capillary Condensation (MTPCCC) is presented. The examples of shift of phase envelopes are presented for selected composition of gas-condensate systems.

PL

Gaz ziemny z łupków (NGS) oraz z ze złóż niskoprzepuszczalnych (typu ‘tight’) staje się jednym z najważniejszych zasobów paliw kopalnych, w tym i następnym dziesięcioleciu. Znaczący wzrost zużycia gazu we wszystkich regionach świata zaznacza się głównie w sektorze energetycznym. Rozpoznawanie niekonwencjonalnych złóż gazu ziemnego i ropy naftowej w ostatnim czasie jest omawiane w wielu konferencjach. Niniejszy artykuł opisuje złożone zjawiska związane z wpływem adsorpcji i kapilarnej kondensacji w nanoporach w złożach gazowo-kondensatowych. Pokazano nowy dwufazowy model równowagowy dwufazowy i nowy algorytm wyznaczania krzywej nasycenia w obszarze kondensacji kapilarnej. Algorytm bazuje na kryterium zmodyfikowanym płaszczyzny stycznej dla kapilarnej kondensacji (MTPCCC). Przykłady zmiany krzywych nasycenia są przedstawiane w wybranym składzie systemów gazowo- kondensatowych.

2

Parametrization of Molecular-Based Equations of State: The PC-SAFT, soft-SAFT, PHSC and PSCT Models

Castro-Marcano F., Colina C., Olivera-Fuentes C.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 1

37-49

EN

We examine the parametrization of four molecular-based equations of state (MBEOS): PC-SAFT, soft-SAFT, PHSC and PSCT. In each case, scaled critical and saturation properties are calculated and related to critical temperature Tc, critical pressure Pc and acentric factor omega through equivalent polynomial expressions. A parametrization strategy matching experimental data of Tc, Pc and omega gives good fits of saturation pressures, but deviations in saturated liquid densities reflect the limitations of each MBEOS in representing the critical region. Nevertheless, the method presented provides a simple way to determine the MBEOS parameters for a wide variety of fluids and can be extended to other models.

3

Numerical Algorithms for Determination of Retrograde Region of Gas Condensate Reservoir

Tarom N., Jalali F., Al-Sayegh A., Moshfeghian M.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 1

51-64

EN

Twomathematical algorithms based on a cubic EOS are developed to determine the retrograde region for reservoir fluids. The first method is based on marching and the second one utilizes regression analysis. In marching method, a series of flash calculations is performed to calculate maximum L/F (moles of liquid/moles of feed). In the regression method, a non-linear regression and an optimizationmethod in addition to a limited number of flash calculations are used to determine the maximum L/F. Based on these mathematical algorithms a computer program to predict a full phase envelope containing the retrograde curve was developed. The computer program consists of three basic parts of bubble point, dew point, and flash calculations. These three basic parts are used to determine the retrograde region. In the course of determination of the retrograde condensation region, the coordinates of critical point and cricondentherm point were also determined and used to speed up the search method. Several cases were studied and it was found that the regression method is faster and more accurate.