Carbonate Pore Systems Abstracts June 25-29, 2017 Austin, Texas USA 2017 Mountjoy Conference-Carbonate Pore Sysrtems Pore system heterogeneity: Impact on reservoir modeling and field development Hisham Alqassab*, Shawn Fullmer, Manal Alharbi, PJ Moore, and Brian Kelly *ExxonMobil, 22777 Springwoods Village, Spring, TX, 77389, USA e-mail: [email protected] Pore system heterogeneity has a profound influence on hydrocarbon displacement, water movement and ultimate recovery. Understanding the relationship between pore type distribution and its influence on both static (porosity and permeability) and dynamic (capillary pressure and relative permeability) properties is critical to understanding reservoir performance. The results of this study demonstrate the benefits of an integrated approach to pore system characterization, dynamic integration, and reservoir modeling that led to an improved match to historical water movement with implications for field development. The ratio of micro-pore space to interparticle pore space in a given unit of rock is a fundamental control on fluid flow. Rocks with a higher proportion of microporosity (>80%—micro-pore dominated) have systematically lower negative capillary pressure (Pc) and lower relative permeability (Kr) to water at a given water saturation than rocks with a lower proportion of microporosity (50–80%—mixed pore system). This translates to more favorable water movement in mixed pore system rocks that are already preferential pathways for water due to higher absolute permeability. Two dynamic rock types were identified based on these observations replacing the 15 rock types utilized in previous modeling efforts. Mixed and micro-pore dominated rock types were identified at wells using core data and PLT calibration and distributed between wells using standard geostatistical techniques. Permeability was modeled using transforms from core data by rock type. The magnitude and distribution of permeability for mixed pore system rock types closely resembles permeability derived from pressure build-up tests at multiple wells providing dynamic validation of the distribution. A special core analysis (SCAL) framework was developed based on the relationship between percent fraction microporosity and Pc, Kr behavior. The resulting reservoir model was simulated to test a variety of scenarios to evaluate the performance differences between the pore system based characterization with mixed and micro- pore rock types presented here and the previous history-matched reservoir model. Water movement in the pore system based model is dramatically different than the previous model and results in a better match to historical water cut data. This study has implications for improved reservoir characterization, modeling and field development. 1 2017 Mountjoy Conference-Carbonate Pore Sysrtems Pore network characterization of a tight carbonate reservoir from the Middle East using dynamic and static methods Mohammad E. Alsuwaidi* and J. Frederick Sarg *The Petroleum Institute, Sas Al Nakhal, Abu Dhabi, Abu Dhabi, P.O. Box 2533, United Arab Emirates e-mail: [email protected] This study aims to understand the pore architecture of a tight carbonate reservoir that has high porosity (up to 25%) but very low permeability (up to 1–3 mD) using integrated techniques at different scales. These techniques include core description, petrography, scanning electron microscopy (SEM), QEMSCAN® (Quantitative Evaluation of Minerals and Porosity by Scanning Electron Microscopy), CMS 300® (Core Measurement System), Mercury Porosimetry, Nitrogen Gas Adsorption–Desorption, and Stable isotope analysis. Results show that interparticle porosity between micrite particles is the main interconnected porosity, while high storage is accounted for by the 5–10 µm sized intrapacricle pores within coccoliths and foraminifera. These microfossils were not compacted due to early cementation of the host mudstones and wackestones that held their morphology intact. Stylolite formation created vertical fluid-flow barriers as a result of dissolution of micrite and re-precipitation into diffused cement above and below clay-rich seams in lower porosity zones. Dynamic methods (conventional and special core analyses) were more diagnostic than static microscopic methods due to the small size of pores. SEM visualization provided key information on identification of preserved intraparticle porosity. Stable isotope data indicate early timing of cementation that supported microfossils from being compacted. Hence, this integrated study provides important clues to the origin and preservation of micropores in tight limestone reservoirs 2 2017 Mountjoy Conference-Carbonate Pore Sysrtems Confocal and transmitted light petrography of cementation and grain types in a high- energy upper shoreface to foreshore carbonate strand line, Pleistocene (MIS 5e) West Caicos Island, Turks and Caicos, B.W.I. Steve Bachtel, Charles Kerans, Neil Hurley*, and Nathaniel Miller *Chevron Exploration Technology Co., 1500 Louisiana, Houston, TX 77002, USA e-mail: [email protected] Confocal petrography provides a new tool for the imaging of cements, pores, and internal structures of ooids and composite grains. Blocky cements, as recognized in TL images are highly zoned and display variable fluorescence, similar to zoning observed in CL petrography (controls on the zonation are currently being investigated). Imaging of isopachous cements are also greatly improved. Micritized ooid nuclei (in TL imagery) are observed to have a complex history including previous periods of coating and microborings. Many ooids that appear to have single nuclei in transmitted light actually are composite grains when viewed with confocal microscopy. Boat Cove, West Caicos Island contains a classic vertical section through an upper shore face to foreshore system (MIS 5e). The section provides excellent control on a single sea level cycle that has experienced constant exposure for 129,000 years. This is important because the effects cementation and dissolution of a single exposure event can be isolated and documented without the complexity of overprinted events as seen in the ancient rock record. Cements observed include a coarse, clear blocky cement (low Mg calcite), a finer crystalline blocky cement, an isopachous blocky cement (multi-generational, high-Mg calcite), and rare needle cements (aragonite). The blocky cements are observed in confocal imagery to be scalenohedral in form and highly-zoned. The blocky cements are most common in areas where voids are being dissolved, like in burrows or in finer grained laminae (due to capillary forces). Alveolar structure is observed in foreshore sediments and meniscus fabrics are present throughout the section. The cements are interpreted to be primarily meteoric cements with minor isopachous and mold-filling cements precipitated from marine fluids (probably beachrock). Moldic porosity is common and is represented by partial to total dissolution of ooid cortices. 3 2017 Mountjoy Conference-Carbonate Pore Sysrtems Effects of micropores in limestones and dolostones on seismic rock properties—a review Gregor Baechle*, Gregor Eberli, and Ralf Weger *Consultant, 22510 Oak Mist Lane, Houston, TX 77494, USA e-mail: [email protected] The elastic properties in carbonate rocks are affected by three main factors: pore fluids, composition of the rock framework and pore space texture. It is important to revisit those fundamental controls of elastic rock property relationships for an accurate quantitative interpretation of conventional and unconventional carbonate plays. In this review, we concentrate specifically on the effects of microporosity on elastic properties of seven different carbonate rock datasets in age ranging from Neogene to Devonian age. We also review if the acoustic characterization of microporosity shows a unique correlation to reservoir quality (permeability). The Extended Biot Theory (EBT) is successfully utilized to approximate the Differential Effective Medium (DEM) trend lines of conceptual pore aspect ratios of 0.1, representing the elastic behavior of micropore-dominated limestones and dolostones. Both models are of equal applicability to quantify the effect of micropores on the velocity-porosity relationship. Out of seven carbonate datasets, five formations show a unique relationship with microporosity correlating with high frame flexibity factors (low acoustic velocities at a given porosity) and a low permeability. Two dolomite formations with micropores within a sucrosic fine crystalline texture show as well a correlation with high frame flexibility factors but display relatively high permeability. There is no unique relationship over all our carbonate datasets between frame flexibility factor and mineralogy and/or permeability. Hence, successful quantitative seismic interpretation requires integration of core and log data to put the elastic properties in the context of what drives reservoir performance. Calibrated rock physics models can uniquely identify and predict the low p-wave and s-wave velocity of microporosity dominated facies at a given porosity, hereby emphasizing the potential of improved reservoir characterization using formation specific calibrated rock physics models. 4 2017 Mountjoy Conference-Carbonate Pore Sysrtems Facies and diagenesis on a steep-sided Late Paleozoic isolated platform: Karachaganak Field, Republic of Kazakhstan James W. Bishop*, Steve Bachtel, Alex J. Parker, and Marina Borovykh *Chevron,