Abstract This paper summarizes parts of the strategies that were developed to demonstrate the feasibility of the first miscible sour gas injection project in one of the reservoirs of a cluster of fields in southern Oman. The hydrocarbons in the cluster are contained in carbonate "stringers", which are approximately 100m thick slabs of carbonate floating within salt at depths between 2.5 km to 5 km. Large quantities of sour gas with 3–4% H2S and 10–15% CO2 are available to be used as miscible agents. The cluster is developed in a phased manner. The key objective of phase one, producing via primary depletion, was to gather data from a number of different reservoirs to determine whether a miscible gas injection project is feasible. A balance between early delivery of new oil and the complex subsurface appraisal that takes resources & time is necessary. An example of a workflow that led to the construction of static & dynamic reservoir models with different realizations in one of the fields is described. This includes 3D seismic, well test and PVT data, well logs, correlations and interference testing. Advanced technologies have been utilized to monitor reservoir performance from Phase 1 and to forecast predicted oil recoveries for the miscible gas injection projects. The collection of production data and pressure performance along with appraisal drilling have provided valuable information to allow the reservoir models to be updated. It is illustrated that the emerging data can lead to subsurface concept refinements which have been included in the project design. The subsurface strategies are described as to how the information has been incorporated in the detailed facility design for this first miscible sour gas injection project in Oman. Introduction In the period between 1997 and 2005, Petroleum Development Oman (PDO) has discovered a major new oil province cluster, constituting 8 fields & 11 reservoirs1. The cluster is located in the south of Oman about 80 km from the nearest infrastructure (see Fig. 1a). The hydrocarbons in the cluster fields are contained in carbonate "stringer" reservoirs, which are approximately 100m thick slabs of carbonates floating within salt. They are referred to as stringers because of their stringtype appearance on seismic data; see Fig. 1b. All the fields within the cluster are deep and are characterised by high pressures with sour, light hydrocarbons. The cluster is developed in a staged/phased manner; see Fig. 2a. Each field goes through four stages of development, namely, appraisal & early primary production; full primary development to ideal Gasflood pressure, full miscible Gasflood development and finally gas blowdown via pressure depletion. The key objectives of phase 1 were firstly to start production from the cluster as early as practically possible and contribute to PDO production targets, and secondly to gather vital subsurface information to underpin an investment decision for a follow up development stage2,3. Phase 2 involves full field primary development in certain selected fields & includes the first miscible Gasflood development in Field A, as shown in Fig. 2b. Subsequent phases will involve full field primary development followed by a stepwise implementation of potential miscible gasflooding and ultimately reservoir pressure blowdown. In Phase 1, 4 fields (including field A) are being produced via primary depletion. They were selected based on different criteria (e.g. reservoir continuity, size, GOR, productivity). Although primary depletion provides a robust development, PDO decided to implement a development based on EOR miscible Gasflood at the earliest opportunity since it has the potential to increase the RF from about 10% (via depletion) to as high as 50%. An aggressive project schedule towards first oil was developed but at the same time subsurface learning was incorporated into the project plans. The process used to accomplish this goal is described in previous articles4,5.

How to ensure that miscibility of oil and gas is achieved in each reservoir is a fundamental issue for miscible gasfloods involving different oil reservoirs with varying fluid properties. This paper reports on all the work done to help decide on how to optimally blend available gas such that miscibility can be achieved in all reservoirs with appropriate focus on the first reservoirs to be flooded. These studies have resulted in an investment decision to undertake a miscible gasflood already in 2005, whereas initial production from four reservoirs had only started in March 2004. Main components of this paper are: (1) Design of experiments for a wide spectrum of fluids (from near-critical systems to black oil systems) using miscible sour gas-blends while minimizing cost and the time spent on the experiments. (2) Acquisition, interpretation of the data (3) Utilization of the data for reservoir engineering/design calculations using a consistent approach for a cluster of sour reservoir fluids, (4) Recommendations based on the experimental data and calibrated simulation models.

Background: Recent studies have shown that chemical composition and morphology, rather than anatomy (degree of stenosis), determine atherosclerotic plaque instability and predict disease progression. Current clinical diagnostic techniques provide accurate assessment of plaque anatomy, but have limited capability to assess plaque morphology in vivo. Here we describe a technique for a morphology-based diagnosis of atherosclerosis in the coronary arteries using Raman spectroscopy that can potentially be performed in vivo using optical fiber technology. Methods: Raman tissue spectra were collected from normal and atherosclerotic coronary artery samples in different stages of disease progression (n=165) from explanted transplant recipient hearts (n=16). Raman spectra from the elastic laminae (EL), collagen fibers (CF), smooth muscle cells (SMC), adventitial adipocytes (AA) or fat cells, foam cells (FC), necrotic core (NC), cholesterol crystals (CC), β-carotene containing crystals (β-C), and calcium mineralizations (CM) were used as basis spectra in a linear least squares-minimization (LSM) model to calculate the contribution of these morphologic structures to the coronary artery tissue spectra. Results: We developed a diagnostic algorithm that used the fit-contributions of the various morphologic structures to classify 97 coronary artery samples in an initial calibration data set as either nonatherosclerotic, calcified plaque, or noncalcified atheromatous plaque. The algorithm was subsequently tested prospectively in a second validation data set, and correctly classified 64 (94%) of 68 coronary artery samples. Conclusions: Raman spectroscopy provides information about the morphologic composition of intact human coronary artery without the need for excision and microscopic examination. In the future, it may be possible to use this technique to analyze the morphologic composition of atherosclerotic coronary artery lesions and assess plaque instability and disease progression in vivo.

Background. We have previously shown that Raman spectroscopy can be used for chemical analysis of intact human coronary artery atherosclerotic lesions ex vivo without tissue homogenization or extraction. Here, we report the chemical analysis of individual cellular and extracellular components of atherosclerotic lesions in different stages of disease progression in situ using Raman microspectroscopy. Methods: Thirty-five coronary artery samples were taken from 16 explanted transplant recipient hearts, and thin sections were prepared. Using a high-resolution confocal Raman microspectrometer system with an 830-nm laser light, high signal-to-noise Raman spectra were obtained from the following morphologic structures: internal and external elastic lamina, collagen fibers, fat, foam cells, smooth muscle cells, necrotic core, beta -carotene, cholesterol crystals, and calcium mineralizations. Their Raman spectra were modeled by using a linear combination of basis Raman spectra from the major biochemicals present in arterial tissue, including collagen, elastin, actin, myosin, tropomyosin, cholesterol monohydrate, cholesterol linoleate, phosphatidyl choline, triolein, calcium hydroxyapatite, calcium carbonate, and ii-carotene. Results. The results show that the various morphologic structures have characteristic Raman spectra, which vary little from structure to structure and from artery to artery. The biochemical model described the spectrum of each morphologic structure quite well, indicating that the most essential biochemical components were included in the model. Furthermore, the biochemical composition of each structure, indicated by the fit contributions of the biochemical basis spectra of the morphologic structure spectrum, was very consistent. Conclusion. The Raman spectra of various morphologic structures in normal and atherosclerotic coronary artery may be used as basis spectra in a linear combination model to analyze the morphologic composition of atherosclerotic coronary artery lesions. (C) 2001 Elsevier Science inc. All rights reserved.

We present a nonparametric method of analysis of Raman spectra of coronary artery tissue to classify atherosclerotic lesions. The method correlates the principal component scores of the Raman spectra with the tissue pathology. A data set composed of 97 samples of human coronary artery was used to develop the diagnostic algorithm, and a second data set composed of 68 samples was then used to test this algorithm prospectively. The results show that the algorithm can accurately classify coronary artery tissue into three classes: nonatherosclerotic, noncalcified plaque, and calcified plaque. The accuracy of this classification scheme is comparable to that previously achieved by means of a biochemical analysis of the Raman spectra using the same data.

The dioxygen-reduction mechanism in cytochrome oxidase relies on proton control of the electron-transfer events that drive the process, Recent work on proton delivery and efflux channels in the protein that are relevant to substrate reduction and proton pumping is considered, and the current status of this area is summarized. Carbon monoxide photodissociation and the ligand dynamics that occur subsequent to photolysis have been valuable tools in probing possible coupling schemes for linking exergonic electron-transfer chemistry to endergonic proton translocation. Our picosecond-time-resolved Raman results show that the heme a(3)-proximal histidine bond remains intact following CO photodissociation but that the local environment around the heme a, center in the photoproduct is in a nonequilibrium state. This photoproduct relaxes to its equilibrium configuration on the same time scale as ligand release occurs from Cu-B, which suggests a coupling between the two events and a potential signaling pathway between the site of O-2 binding and reduction and the putative element, Cu-B, that links the redox chemistry to the proton pump.

BACKGROUND:Lesion composition, rather than size or volume, determines whether an atherosclerotic plaque will progress, regress, or rupture, but current techniques cannot provide precise quantitative information about lesion composition. We have developed a technique to assess the pathological state of human coronary artery samples by quantifying their chemical composition with near-infrared Raman spectroscopy.METHODS AND RESULTS:Coronary artery samples (n=165) obtained from explanted recipient hearts were illuminated with 830-nm infrared light. Raman spectra were collected from the tissue and processed to quantify the relative weights of cholesterol, cholesterol esters, triglycerides and phospholipids, and calcium salts in the examined artery location. The artery locations were then classified by a pathologist and grouped as either nonatherosclerotic tissue, noncalcified plaque, or calcified plaque. Nonatherosclerotic tissue, which included normal artery and intimal fibroplasia, contained an average of approximately 4+/-3% cholesterol, whereas noncalcified plaques had approximately 26+/-10% and calcified plaques approximately 19+/-10% cholesterol in the noncalcified regions. The average relative weight of calcium salts was 1+/-2% in noncalcified plaques and 41+/-21% in calcified plaques. To make this quantitative chemical information clinically useful, we developed a diagnostic algorithm, based on a first set of 97 samples, that demonstrated a strong correlation of the relative weights of cholesterol and calcium salts with histological diagnoses of the same locations. This algorithm was then prospectively tested on a second set of 68 samples. The algorithm correctly classified 64 of these new samples, thus demonstrating the accuracy and robustness of the method.CONCLUSIONS:The pathological state of a given human coronary artery may be assessed by quantifying its chemical composition, which can be done rapidly with Raman spectroscopic techniques. When Raman spectra are obtained clinically via optical fibers, Raman spectroscopy may be useful in monitoring the progression and regression of atherosclerosis, predicting plaque rupture, and selecting proper therapeutic intervention.

We are developing optical methods based on near infrared Raman spectroscopy and fluorescence photon migration for diagnosis and localization of breast cancer, We demonstrate the ability of Raman spectroscopy to classify accurately normal, benign and malignant breast tissues, an important step in developing Raman spectroscopic needle probes as a tool for improving the accuracy of needle biopsy, We also show that photon migration imaging can be used to localize accurately small fluorescent objects imbedded in a thick turbid medium with realistic optical properties, thus demonstrating the potential of this technique for optical imaging.

Nonresonant Raman cross sections of ~10 -16 cm 2 per molecule are shown to be related to surface-enhanced Raman scattering (SERS) on colloidal silver clusters at near-infrared (NIR) excitation. The enhancement is found to be independent of cluster sizes between 100 nm and 20 μm. These experimental findings demonstrate that NIR SERS on colloidal silver clusters is an excellent technique for single molecule detection that is applicable for a broad range of molecules including "colorless" biomolecules, for example nucleotides in DNA sequencing. As an example, we present the detection of a single adenine molecule without any labeling based on its intrinsic surface-enhanced Raman scattering.

Single-molecule Raman spectroscopy of a cyanine dye in aqueous silver colloidal solution with the use of surface-enhanced Raman scattering at near-infrared excitation (NIR-SERS) is reported. A characteristic Poisson distribution of SERS signals due to the Brownian motion of single dye molecule-loaded silver particles reflects the probability of finding 0, 1, or 2 1,1'-diethyl-2,2'cyanine (PIC) molecules in the probed volume during an actual measurement and is evidence that single-molecule detection by SERS has been achieved. Spectra measured in 1 s collection time with 100 mW nonresonant 830 nm excitation provide a clear “fingerprint” of a single PIC molecule by showing its typical Raman lines between 700 and 1700 cm−1. Single-molecule Raman signals are also detected for the first time at the anti-Stokes side of the excitation laser. Effective Raman cross sections for PIC of ∼10−16 cm2 per molecule can be inferred from the ratio between “pumped” anti-Stokes and Stokes signals.

Angle-resolved fluorescence depolarization experiments were carried out on 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) molecules embedded in macroscopically oriented multilayers of saturated [dimyristoylphosphatidylcholine (DMPC)] and unsaturated [palmitoyloleoylphosphatidylcholine (POPC), dioleoylphosphatidylcholine (DOPC), dilineoylphosphatidylcholine (DLPC), plant digalactosyldiglyceride (DGDG)] lipids with and without cholesterol. In all the lipid systems studied the order parameter (P2) of TMA-DPH molecules was found to be higher than that for DPH. Considerations of the order parameter (P4), however, indicate that DPH molecules have a heterogeneous distribution in bilayers of unsaturated lipids, with a significant fraction of the molecules lying with their long axes parallel to the bilayer planes. Both the DPH and TMA-DPH molecules exhibit a decrease in the molecular order as well as a decrease in their rates of motion on increasing the unsaturation of the hydrocarbon chains. The addition of cholesterol tends to reverse this effect, with an increase in both the order and dynamics. Bilayers of DOPC, however, exhibit a somewhat different result. It is suggested that the discrepancies between these observations and findings with lipid vesicle systems simply reflect the effects of curvature on the behavior of the probe molecules. The results indicate that the concept of membrane fluidity must be used with great caution.

Author Institution: Departments of Chemistry and the LASER Laboratory, Michigan State University