2010 SPWLA Topical Conference Integration of Reservoir Rock Types in Simulation Models Shawket Ghedan, PhD Petroleum Institute Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models Development and Identification of RRTs Reservoir Rock Types, RTTs developed by integrating: Petrophysical Lab data, Pore system information, and Capillary Pressure Data. RRTs can be identified by the following parameters: Rock Fabric: texture, grain size, packing & pore geometry Proportion of primary porosity and secondary porosity. Porosity/ permeability relationships Range of, and similarity in pore throat size distribution, Similar Pc curves and saturation end points. Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models RRTs in Static and Dynamic Models Static RRTs are routinely employed for: Modeling of reservoir petrophysical attributes, as well as Building & assigning the required water/ oil and Gas/ oil Kr curves to the different cells of the simulation models. There is a problem with the second application: Static RRT schemes do not consider the reservoir multiphase flow properties of wettability, fluids IT, etc… Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models Static vs Kr-Defined RRTs Hamon introduced the Kr-defined rock types (SPE 84035, 2003 ATCE). Definition of Kr-Defined Rock Types: Kr-defined rock types are defined as units of rock characterized by similar ranges of pore geometry and wettability indicators resulting in a unique relative permeability saturation relationships. Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models Kr-Defined RRTs or Dynamic RRTs For the same saturation history cycle in a reservoir, the rock multiphase flow properties would only be a function of wettability only for any static RRT. In a reservoir with a wettability profile, each RRT would have many Wettability Driven Dynamic RRTs. Therefore, imposing the effect of reservoir wettability on the RRTs is essential in developing and assigning the Kr curves to the cells of simulation models. Each would have unique relative permeability curves and saturation endpoints. Feb 10 Integration of RRTs in Sim Models

USBM WI vs Depth from Well A of Hawiyah area SPE 105114 SPE 105114 Feb 10 Integration of RRTs in Sim Models

USBM WI versus Depth from Well B of Hawiyah area SPE 105114 SPE 105114 Feb 10 Integration of RRTs in Sim Models

USBM WI versus Depth for Uthmaniyah area SPE 105114 Feb 10 Integration of RRTs in Sim Models

Reservoir Wettability Profile Wells perforations Producers down to X000 ftss Injectors up to X150 ftss Wettability Oil Wet at Top structure Water Wet Below DOL. Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models Transition Zone? Transition zones in Carbonate reservoirs could be fairly thick. depending on reservoir characteristics. Transition zone is conventionally defined as that part of the reservoir where water saturation start to deviate from irreducible saturation down to 100% saturation. Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models Dry Oil Limit 300 oil producers, screened to identify Deepest perforations of dry oil producers, and Static RRTs of their producing layers. From Which Identified the Dry Oil Limit of the reservoir RRTs. Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models Alternative Definition of TZ DOL for any rock type was found to be always appreciably deeper than the top of the conventional transition zone. The difference depends on the rock types encountered and profile of rock wettability changes. Transition zone is better defined as the reservoir part where both phases of oil and water are mobile. Feb 10 Integration of RRTs in Sim Models

Requirements of Saturation Tables Log-derived W/O Pc curves. Swirr at top of structure, Swc at Dry Oil Limit Feb 10 Integration of RRTs in Sim Models

History Matching of Available Exp Kr Data Use Corey Model for history matching For various RTs determined No and Nw with Depth Feb 10 Integration of RRTs in Sim Models

History matching of Available Exp Data Exp Kr data for RT1 No and Nw variation with Depth Feb 10 Integration of RRTs in Sim Models

History Matching of Exp Data Poor Limestone RT8 No and Nw variation with Depth Feb 10 Integration of RRTs in Sim Models

Variation of Corey Exponents Poorer RTs Increasing Depth Porosity No Increase Decrease Constant Nw Increase Increase Constant No = (2.8 to 5.0) Nw = (1.3 to 2.6) Feb 10 Integration of RRTs in Sim Models

Correlation of Sorw vs. Swi or Swc Feb 10 Integration of RRTs in Sim Models

Correlation of Sorw vs. Swi or Swc A correlation is developed to relate Sorw to Swc. For Each Rock Type Swc ranges: From Swirr, at the top of the reservoir, to Sw value at the DOL level (top of the transition zones) Feb 10 Integration of RRTs in Sim Models

Effect of Wettability on Krwmax and Sorw It is well established that Sorw as well as Krwmax at Sorw would be lower for more water wet rock. From Dave Bowen of Core Lab Feb 10 Integration of RRTs in Sim Models

Impact of Wettability on End Points of Kr Curves From Dave Bowen of Core Lab From Dave Bowen of Core Lab Feb 10 Integration of RRTs in Sim Models

Integration of RRTs in Sim Models Krwmax versus Sorw The available data did not yield clear relationship between Krw(Sorw) Vs Sorw But a straight line relationship was forced that fits the general trend of the data. Feb 10 Integration of RRTs in Sim Models

Number of DRRTs Per Static RRT The number of DRRTs generated per each SRRT is decided by the number of the Sw increment employed to go from Swirr down to Swc at the DOL of each drainage Pc curve of each static RRT. For instance, using a 5% Sw increment with seven maximum steps would produce up to 21 DRRTs (Kr sets) for each static RRT. Feb 10 Integration of RRTs in Sim Models

Generation of DRRTs (Kr Curves) 1. For each depth, Swc is picked from any drainage Pc curve, ranging from Swirr up to Swc at DOL, then: 2. Use Swc to determine Sorw from the proposed correlations, similar to Land correlation 3. Use depth and rock type to determine Corey’s exponents, Nw and No, using a table look up. 4. Use Sorw to determine Krwmax from the proposed correlation (Kromax is taken as 1.0): Feb 10 Integration of RRTs in Sim Models

Generation of Kr Curves 5. Use the Corey Krw and Kro models to determine Krw and Kro for any water saturation between any Swc and its Sorw. Feb 10 Integration of RRTs in Sim Models

Generation of Kr Curves Set of Kr curves for Limestone RRT 4 of 15% porosity. Feb 10 Integration of RRTs in Sim Models

2010 SPWLA Topical Conference ? Feb 10 Integration of RRTs in Sim Models