Pressure and Compositional Gradients in Reservoirs

Abstract

Pressure and Compositional Gradients in Reservoirs F. Montel; F. Montel TOTAL Search for other works by this author on: This Site Google Scholar J. Bickert; J. Bickert TOTAL Search for other works by this author on: This Site Google Scholar J. Hy-Billiot; J. Hy-Billiot TOTAL Search for other works by this author on: This Site Google Scholar M. Royer M. Royer TOTAL Search for other works by this author on: This Site Google Scholar Paper presented at the Nigeria Annual International Conference and Exhibition, Abuja, Nigeria, August 2003. Paper Number: SPE-85668-MS https://doi.org/10.2118/85668-MS Published: August 04 2003 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Montel, F., Bickert, J., Hy-Billiot, J., and M. Royer. "Pressure and Compositional Gradients in Reservoirs." Paper presented at the Nigeria Annual International Conference and Exhibition, Abuja, Nigeria, August 2003. doi: https://doi.org/10.2118/85668-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Nigeria Annual International Conference and Exhibition Search Advanced Search AbstractThe search for the optimal development of a field involves proper knowledge of the composition of the fluids that impregnated the reservoirs. The development scheme could be strongly affected by the connectivity between the different reservoir units. After their migration into the trap, the fluids are shaped by various forces, among them, gravity has the most striking effect and was widely studied. In many cases there is evidence for the contribution of other forces like thermal gradients. Taking into account all the phenomena, to establish a consistent picture of fluids distribution in the field is an important challenge for the petroleum industry. Reciprocally the actual fluid distribution can be used to assess the connectivity of the different panels and layers. In that case, all the possible compositional redistribution mechanisms have to be taken into account.In some circumstances, particularly in recent mature and permeable petroleum systems, hydrocarbon accumulations are subjected to gas fluxes, which lead to non-conventional fluid distribution. There are already a number of tools available for calculating the compositional gradient within a reservoir, including the contribution of gravity and thermal gradient. In many field cases, however, the calculated profile differs from actual. The discrepancies are input to another external force: the mass flux of light component at the reservoir boundaries.In this paper, the authors present the modeling of diffusion fluxes across the reservoir and point out how the diffusion fluxes can reveal the permeability barriers through the pressure and the compositional profiles.Drawing on a field example, this paper provides a methodology for dealing with dynamic reservoir fluid systems. The model matches the observed compositional gradient and corresponding PVT properties. It allows reliable connectivity assessment in cases where gravitational modeling fails.IntroductionThe PVT properties of the various samples taken from a reservoir may be very different. Although accurate knowledge of each sample is necessary, this does not usually extend in obvious fashion to the reservoir as a whole. Therefore, reservoir fluid evaluation is compulsory as a preliminary study before any development plan and it must be updated regularly during the life of the field. All the fluid data are required to reach a comprehensive knowledge of the fluid system and many complementary reservoir data as pressure, temperature and logs are essential.Gravity segregation models allow us to calculate the composition of the fluid at any depth in the reservoir fluid column from the composition at a reference depth, just by adding the gravity contribution to the chemical potential of the components[1–4]. This option is now included in most of the PVT software's. Unfortunately in many field cases, the actual compositional profile cannot be obtained with this single external force. The capillary forces can lead to significant differences in the case of two-phase reservoirs[5–6] and the thermal field is obviously responsible for part of the discrepancies[7–12] but the most striking difference certainly comes from the dynamic situation of the reservoirs[13–17]. Keywords: flux, fluid column, montel, upstream oil & gas, permeability barrier, caprock, fluid modeling, permeability, methane flux, spe 85668 Subjects: Fluid Characterization, Fluid modeling, equations of state This content is only available via PDF. 2003. Society of Petroleum Engineers You can access this article if you purchase or spend a download.