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.

Assessment of Radius of Investigation of Pressure Transient Analysis in Highly Heterogeneous Reservoirs

The radius of investigation (ROI) of pressure transient analyses has been traditionally assessed using analytical formulations with basic reservoir parameters for homogenous systems. Numerous studies aimed to improve ROI formulations to incorporate all reservoir and testing parameters such as gauge resolution and rate for more accurate ROI assessments. However, new generation wireline formation testers aim to improve deep transient tests with significant developments in gauge resolution and increasing rate. Challenges still remain in heterogeneous formations such as shaly sands and carbonate reservoirs. In this study, detailed conceptual high-resolution numerical models are set up, including comprehensive reservoir and measurement parameters, to investigate more realistic ROI assessments in layered heterogeneous systems without and with hydraulic communication. Several conceptual examples are presented in layered systems with permeability contrasts. In addition, deviation from infinite-acting radial flow (IAFR) and pressure propagation in highly heterogeneous layered systems are investigated to detect the presence of geological features, including closed boundary systems and the presence of a fault in the proximity of wellbore.

Machine learning based approach for the interpretation of engineering geophysical sounding logs

In this paper, a set of machine learning (ML) tools is applied to estimate the water saturation of shallow unconsolidated sediments at the Bátaapáti site in Hungary. Water saturation is directly calculated from the first factor extracted from a set of direct push logs by factor analysis. The dataset observed by engineering geophysical sounding tools as special variants of direct-push probes contains data from a total of 12 shallow penetration holes. Both one- and two-dimensional applications of the suggested method are presented. To improve the performance of factor analysis, particle swarm optimization (PSO) is applied to give a globally optimized estimate for the factor scores. Furthermore, by a hyperparameter estimation approach, some control parameters of the utilized PSO algorithm are automatically estimated by simulated annealing (SA) to ensure the convergence of the procedure. The result of the suggested ML-based log analysis method is compared and verified by an independent inversion estimate. The study shows that the PSO-based factor analysis aided by hyperparameter estimation provides reliable in situ estimates of water saturation, which may improve the solution of environmental end engineering problems in shallow unconsolidated heterogeneous formations.

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.

Deviated Drilling Through Salt Dome and Horizontalization Across Extremely Heterogeneous Formations: A Case Study in North Abu Dhabi

Over the last 60 years, Abu Dhabi, United Arab Emirates (UAE) has been producing oil and gas from different conventional fields. Nowadays, and as part of the State long-term strategy to achieve the nation objective of gas self-sufficiency, it has been decided to explore, appraise and develop unconventional plays in the Northern area including the construction of early production facilities to supply the gas power plants. Three wells were drilled as part of the first phase of the project; consisting of a pilot hole into an extremely heterogeneous formation; two of them were horizontalized into the targeted formations. The first well across the salt represented a tremendous challenge due to limited rig capacity generating hole stability issues that required unplanned remedial jobs. The second well was deviated across the salt as pilot hole, then side-tracked and horizontalized in the targeted reservoirs. The third well was drilled directly as horizontal lateral based on previous lessons learned validating the horizontal concept for the future field development plan. The exploration phase constituted by these three wells, were drilled and completed successfully. A detailed data gathering program was executed allowing mapping of the area validating the presence of gas. The drilling parameters, such as rate of penetration (ROP) for the horizontal section was enhanced by optimizing the drilling Bit design. The mud logging results have confirmed the extremely heterogeneous formations across this section allowing determining the most fit for purpose bottom hole assembly (BHA); obtained after a detailed optimization process. Multiple lessons learned were captured and immediately applied leading to a significant reduction on total days per well that reflected on an outstanding cost reduction including rig move optimization, incrementing the overall efficiency of the operations. This project has proven the potential of unlocking the development of this field focusing on the targeted untapped reservoirs. Key unprecedented achievements have been fulfilled during the execution of this phase of the project: 1. First time to drill across a salt dome in Abu Dhabi Emirate 2. First time that horizontalization has been applied to the targeted formations. In addition, a better understanding of the optimum drilling parameters for future phases has been obtained.