A Practical Model for Water Injection Evaluation and Optimization in Typical Offshore Reservoirs Considering Formation Heterogeneity Based on Experimental Study

A major concern with water injection in offshore oil reservoir is the water breakthrough. The formation heterogeneity is the main reason for it. In order to evaluate the water injection efficiency, a visualized 2-D experiment was carried out to obtain the distribution law of injected water and the variation of injection parameters in homogeneous and heterogeneous formation. In addition, a coupled wellbore/reservoir model was established by applying microelement method, superposition principle and imaging. This model considers the formation heterogeneity and pressure drop caused by wellbore friction. The visualized 2-D sand filling displacement experiment indicates that the injection rate at the horizontal well heel is greater than that at the toe and the injection front is more irregular in heterogeneous formation. The injection rate and injection pressure distribution along the horizontal well are obtained analytically based on the proposed model, the results show that the injection rate at the two sides of the wellbore is much higher than that in the middle when the formation is homogeneous and the wellbore is infinite-conductive. In this case, the injection rate curve along horizontal well shows a "U" shaped distribution. When a finite-conductive horizontal wellbore is considered, the injection rate at the heel of the wellbore is higher than that of the toe, although the injection rate curve along horizontal well also exhibits a deformed "U" shape distribution. For the formation heterogeneities along the horizontal wellbore, the injection rate distribution curve is not continuous anymore, but a deformed "U" shape is also observed for each wellbore segment. At last, the established model was applied to an ultra-heterogeneous offshore reservoir. It is concluded that the profile control effect of typical well is obvious. The results of this study are of great significance for the calculation of the injection rate profile and improving the water injection efficiency.

First Application of Hybrid Bit Technology to Optimize Drilling Through S Shape Directional Section with High Chert Content in UAE Land Operations

This paper highlights the solution, execution, and evaluation of the first 12.25″ application of hybrid bit on rotary steerable system in S-Shape directional application to drill interbedded formations with up to 25 % chert content in UAE land operations. The main challenge that the solution overcame is to drill through the hard chert layers while avoiding trips due to PDC bit damage nor drilling hour's limitation of TCI bit while improving the overall ROP and achieving the directional requirement. The solution package has demonstrated a superior ROP over rollercone bits, as well as improved PDC cutter durability and lower reactive torque leading to better steerability and stability which will be detailed in this paper. A significant contributor to such success was utilizing a new hybrid bit technology which incorporates the dual cutting mechanisms of both polycrystalline Diamond Compact (PDC) and rollercone bits. This allows a more efficient drilling by bringing the durability of the crushing action of rollercone to drill through hard interbedded lithology and the effectiveness of the shearing action of PDC cutters to improve ROP without sacrificing the toughness of the cutting structure edge. The proposed solution in combined with continues proportional rotary steering system managed to drill 4,670 ft through heterogeneous formation with chert nodules, with an average ROP of 38.29 ft\hr improving ROP by 15% and eliminating extra trips of utilizing roller cone bits to be able to drill though the chert nodules and avoid the PDC bit damage. Leading reduction in cost per foot by 35 %. Additionally, the hybrid bit exceed the expectation achieving 878 thousand of revolutions, with effective bearing and with the drilling cutting structure in a very good condition. Furthermore, the directional objectives were met with high quality directional drilling avoiding wellbore tortuosity. Such success was established through application analysis, specific formations drilling roadmaps and optimized drilling parameters in order to improve the overall run efficiency. The combination of roller cone and PDC elements in a hybrid bit designed to deliver better efficiency and torque stability significantly increased performance drilling the section in one single run, proven that heterogeneous formations can be drill.

Formation Heterogeneity Effect on Steam Injection and Propagation

The objective of this work is to evaluate and understand steam injection in heterogonous formation utilizing a state-of-the-art experimental apparatus. Heat transfer and efficiency for steam injection are evaluated in heterogeneous formation and compared with homogenous formation. The information obtained from the apparatus provided the key in designing effective steam injection for optimized recovery in heterogeneous formations. This paper presents several successful experimental works and proposes solutions to overcome the challenges produced from heavy oil reservoirs. The technology utilizes advanced thermal apparatus to improve heat penetration depth into the formation and efficiency of the thermal heating. Steam is the most used technology due to its high latent heat capacity, cost and maturity. Steam injection should be carefully planned to ensure the injectivity to the target. Heterogeneity adds to the complexity of the operation, as the steam will propagate in different orientations. This study provides the key element to understand steam propagation to maximize the recovery efficiency. The experiments were carried out using heavy oil apparatus, which is designed to accurately simulate reservoir conditions. It measures one meter in length by one meter in width by one and a half meter in height. It has 65 thermocouples, 24 acoustic transducers, 9 vertical wellbores, 9 horizontal wellbores; these data are used for modeling and simulation. The apparatus can use sand or blocks. Thermal technology is very effective to mobilize heavy and viscous oil; steam injection has been successfully and widely deployed due to its reasonable cost, maturity, and efficient thermal transfer to reservoir fluids. Understanding the formation is vital to ensure successful steam-based stimulation, especially in heterogonous reservoirs. To this end, an apparatus was designed to evaluate steam injection in heterogonous formations. This is one-of-a kind studies that evaluates heterogeneity effect at a large scale and provides detailed analysis. First, steam is injected in homogenous formation to establish a baseline of heat propagation in formation. Second, the apparatus is filled in layers resembling a heterogonous formation, and steam is injected at same conditions (i.e., wellbore depth and injection rate and pressure). The device collected a real-time temperature map using 65 thermocouples. 3D graph and animations are plotted to visualize and evaluate the pattern and trend of steam propagation in both homogenous and heterogeneous formations. The apparatus is uniquely deigned to evaluate different scenarios that simulate the field and wellbores more accurately. Due to its volume (one cubic meter), the device is the largest apparatus in literature, and flexibility, the device enables the replication of a heterogeneous formation. The amount of data and information gathered, make the apparatus unique and provide key elements to drive successful steam injection operations.

Isotopic evidence for dominant secondary production of HONO in near-ground wildfire plumes

Nitrous acid (HONO) is an important precursor to hydroxyl radical (OH) that determines atmospheric oxidative capacity and thus impacts climate and air quality. Wildfire is not only a major direct source of HONO, it also results in highly polluted conditions that favor the heterogeneous formation of HONO from nitrogen oxides (NOx= NO + NO2) and nitrate on both ground and particle surfaces. However, these processes remain poorly constrained. To quantitatively constrain the HONO budget under various fire and/or smoke conditions, we combine a unique dataset of field concentrations and isotopic ratios (15N / 14N and 18O / 16O) of NOx and HONO with an isotopic box model. Here we report the first isotopic evidence of secondary HONO production in near-ground wildfire plumes (over a sample integration time of hours) and the subsequent quantification of the relative importance of each pathway to total HONO production. Most importantly, our results reveal that nitrate photolysis plays a minor role (<5 %) in HONO formation in daytime aged smoke, while NO2-to-HONO heterogeneous conversion contributes 85 %–95 % to total HONO production, followed by OH + NO (5 %–15 %). At nighttime, heterogeneous reduction of NO2 catalyzed by redox active species (e.g., iron oxide and/or quinone) is essential (≥ 75 %) for HONO production in addition to surface NO2 hydrolysis. Additionally, the 18O / 16O of HONO is used for the first time to constrain the NO-to-NO2 oxidation branching ratio between ozone and peroxy radicals. Our approach provides a new and critical way to mechanistically constrain atmospheric chemistry and/or air quality models on a diurnal timescale.

Atmospheric Measurements at the Foot and the Summit of Mt. Tai – Part I: HONO Formation and Its Role in the Oxidizing Capacity of the Upper Boundary Layer

A comprehensive field campaign, with measurements of HONO and related parameters, was conducted in summer 2018 at the foot (150 m a.s.l.) and the summit (1534 m a.s.l.) of Mt. Tai (Shandong province, China). At the summit station, high HONO mixing ratios were observed during this campaign (mean ± 1σ: 133 ± 106 pptv, maximum: 880 pptv), with a diurnal noontime peak (mean ± 1σ: 133 ± 72 pptv at 12:30 local time). Constraints on the kinetics of aerosol-derived HONO sources (NO2 uptake on the aerosol surface and particulate nitrate photolysis) were performed and discussed, which enables a better understanding of the interaction of HONO and aerosols, especially in the polluted North China Plain. Various shreds of evidence of air mass transport from the ground to the summit levels were provided. Furthermore, daytime HONO formation from different paths and its role in radical production were quantified and discussed. We found that the homogeneous reaction NO + OH could only explain 8.0 % of the daytime HONO formation, resulting in strong unknown sources (Pun). Campaigned-averaged Pun was about 290 ± 280 pptv h−1 with a maximum of about 1800 pptv h−1. Aerosol-derived HONO formation mechanisms were not the major sources of Pun. Their contributions to daytime HONO formation varied from negligible to moderate (similar to NO + OH), depending on the used chemical kinetics. Coupled with sensitivity tests on the used kinetics, the NO2 uptake on the aerosol surface and particulate nitrate photolysis contributed 1.5–19 % and 0.6–9.6 % of the observed Pun, respectively. Based on synchronous measurements at the foot and the summit stations, a bunch of field evidence was proposed to support that the remaining majority (70–98 %) of Pun was dominated by the rapid vertical transport from the ground to the summit levels and heterogeneous formation on the ground surfaces during the transport. HONO photolysis at the summit level initialized daytime photochemistry and represented an essential HOx (OH + HO2) source in the daytime, with a contribution of 26 %, more than one-third of that of O3. We provided evidence that ground-derived HONO played a significant role in the oxidizing capacity of the upper boundary layer through the enhanced vertical air mass exchange driven by mountain winds. The follow-up impacts should be considered in the regional chemistry-transport models.

Characterization of Degenerate Configurations in Attitude Determination of Three-Vehicle Heterogeneous Formations

The existence of multiple solutions to an attitude determination problem impacts the design of estimation schemes, potentially increasing the errors by a significant value. It is therefore essential to identify such cases in any attitude problem. In this paper, the cases where multiple attitudes satisfy all constraints of a three-vehicle heterogeneous formation are identified. In the formation considered herein, the vehicles measure inertial references and relative line-of-sight vectors. Nonetheless, the line of sight between two elements of the formation is restricted, and these elements are denoted as deputies. The attitude determination problem is characterized relative to the number of solutions associated with each configuration of the formation. There are degenerate and ambiguous configurations that result in infinite or exactly two solutions, respectively. Otherwise, the problem has a unique solution. The degenerate configurations require some collinearity between independent measurements, whereas the ambiguous configurations result from symmetries in the formation measurements. The conditions which define all such configurations are determined in this work. Furthermore, the ambiguous subset of configurations is geometrically interpreted resorting to the planes defined by specific measurements. This subset is also shown to be a zero-measure subset of all possible configurations. Finally, a maneuver is simulated to illustrate and validate the conclusions. As a result of this analysis, it is concluded that, in general, the problem has one attitude solution. Nonetheless, there are configurations with two or infinite solutions, which are identified in this work.

Laboratory studies of the oil-displacing capacity of multifunctional chemical composition based on surfactants

The development of deposits of hard-to-recover reserves, including heavy and high-viscosity oil, dictates the need to search for new and improve existing enhanced oil recovery methods. One of the well-known methods of increasing oil recovery is the use of reservoir treatments with chemical compositions containing surfactants. A new multifunctional chemical oil-displacing composition (MFC) capable of operating in a wide temperature range has been created at the Institute of Petroleum Chemistry, Siberian Branch of the Russian Academy of Sciences. The oil-displacing composition of MFC based on a surfactant, an adduct of inorganic acid, polyol, ammonium and aluminum salts, and urea is designed to increase the oil recovery of fields at both early and late stages of development.The article presents the results of laboratory tests of the developed MFC for enhanced oil recovery. Experiments were carried out on the setup to study the filtration characteristics of models of heterogeneous formation.As a result of experiments, it was found that the use of the MFC composition leads to a significant increase in the oil displacement coefficient at both low and high temperatures. The high oil-displacing capacity of MFC at low temperature is caused by the interaction of inorganic acid and polyol, which are part of the composition, with the formation of a strong acid that reacts with the carbonate rock of the reservoir. At high temperature, due to the processes of hydrolysis of urea and aluminum salt, MFC evolves into an alkaline composition with the formation of an alkaline buffer system (pH = 9), which is optimal for oil displacement purposes.