Multistage Acid Stimulation for ICD Screens Completion Using Straddle Packer and Real-Time Telemetry Coil Tubing

Inflow Control Devices (ICD) (Fig. 1) is a part of the well completion to help optimizing the production by equalizing the reservoir inflow. Multiple ICD can be installed in the completion at a long section, as each ICD going to partially choke the flow. Completing wells with ICD is one of the most common techniques that is used to maintain uniform production across multi-layer reservoirs. One of the challenges in such completions is to achieve a uniform matrix acid stimulation across these screens due to well deviation and length of the screens. In most cases an effective diversion method is required during acid treatment to ensure all the screens are treated uniformly for maintaining homogeneous production across the reservoir. Over the time, wells with ICD screens show decline in production due to plugged screens which necessitates immediate action. In most cases remedy is to acid treat all ICD screens on individual basis using straddle packer System and real-time telemetry coil system due to requirements of diversion method, criticality of the packer setting depth and downhole pressure monitoring. Multistage acid stimulation for ICD screens is achieved using straddle packer's system with real-time telemetry coiled tubing (CT). The real-time telemetry coil system ensures depth accuracy – as each ICD port length is not more than couple of inches – and monitoring of pressures and straddle packer system's integrity during multistage acid stimulation across the horizontal screens. This operation involves challenges of properly setting the packer to selectively treat each ICD screen by mechanically diverting the acid treatment while maintaining seal integrity in each stage and re-using it multiple times. After drifting and wellbore conditioning run, the multi-set straddle packer system is deployed on real-time telemetry coil (fiber-optic enabled) for multistage acid treatment. Starting from total depth, the real-time CCL readings are utilized successfully to identify the first screens joint allowing the packer system to be stationed across the required screen. The packer elements are then energized to divert the acid treatment fluid into the targeted screen Thru the coil and exiting from per adjusted nozzles between the Packers; this diversion is confirmed by monitoring bottom hole pressure inside and outside the coil tubing string. Upon completion of the acid treatment of the ICD screens the tension-compression sub of telemetry coil system confirmed the elements is de-energized to make safe to move the packer without damaging the elements. The treatment is then successfully repeated across the remaining ICD screens with positive indication of diversion across each ICD screen. This study illustrates how the combination of the straddle packer System and downhole real-time telemetry system was utilized to successfully acid stimulate up to 38 stages and monitor the behavior of straddle packer continuously during diversion of multistage acid treatment of screens while maintaining packers seal integrity and downhole pressures. In addition, the study also provides lessons learned from implementation of multi-stages packers with real-time telemetry for successful diversion of acid treatment uniformly across the screens in horizontal well.

Development, Evolution, and Episodic Charge History of Pop-up Structures in Southeast Abu Dhabi, UAE

The main goal of this paper is contributing to the understanding to the structural geology, development, and evolution of traps associated with strike-slip restraining bend and restraining step-over structures as a key petroleum system element in southeastern Abu Dhabi. We introduce a preliminary classification scheme for these relatively small, low-relief features defined here as pop-up structures. These structures represent different evolutionary stages of strike-slip restraining bends formed along prominent WNW-trending strike-slip fault systems in southeastern Abu Dhabi. The proposed classification scheme was summarized as a chart to illustrate the correlation between the degree of structural deformation and seal integrity, and estimates the likelihood of finding multiple, vertically stacked, productive reservoirs. It also leads to a more detailed discussion on others important characteristics of pop-up structures and provides a better understanding of sealing mechanisms such as fault juxtaposition, fault throw analysis, fault slip tendency, fault rock processes, and the role of the development of hybrid flower structures in the area. We will also show a simple case study based on two exploratory wells that targeted two pop-up structures with different degrees of deformation in southeast Abu Dhabi. This case study illustrates the complex relationship between pop-up evolution, timing of trap formation, seal integrity, trap preservation, and multiple petroleum generation and migration events. Pop-up structures are linked to multiple episodes of trap and seal evolution, where several episodes of hydrocarbon migration, charge, and leaking of hydrocarbons may occur.

Reducing Gas Emission Mechanisms for Hydrocarbon Storage Tanks

Volatile Organic Compounds (VOC) which are emitted from tank farms of petroleum refineries are considered to cause harmful impacts to the environment and people. This paper presents the methodology of assessing potential targets for reduction of emissions, as well as proposed control mechanisms and their reductions, for hydrocarbon storage tanks at Jebel Al Dhanna Terminal. Some of the emissions reduction opportunities which are covered include aluminum dome retrofits, seal integrity improvement and guide pole treatments. The objective is to find significant reduction opportunities (from between 50% to 90% of current tank configurations) using passive technologies which prevent or inhibit emissions without the use of additional operational energy or active systems that would otherwise require significant maintenance or operational expense.

Sealing Mechanism Based on Force Chain and Experimental Investigation of Sealing Fractures

Lost circulation often occurs in fractured formations, which was a main technological problem during drilling. Conventional lost circulation material (LCM) was often used to form a plugging zone to prevent fluid loss during drilling. The formed seal was a granular material system composed of LCMs. This paper presented the physical mechanism of the force chain within the plugging zone. The seal performance is related to the properties of LCMs. A device for testing seal performance of LCMs with long fracture was developed. The effects of LCM performance on seal integrity were investigated using a plugging device with long fracture. The results showed that the wide particle size distribution (PSD) of LCMs tended to form a strong force chain network structure within the sealing zone. Increasing the stiffness and roughness of LCMs resulted in higher breaking pressure. The addition of fiber with high length-diameter ratio could improve the shear strength of the sealing zone and form a strong force chain network structure, and it can reduce fluid loss.

Downhole Monitoring of Fractures in a Waterflood Development – Part II

For maintenance of the reservoir pressures and enhanced oil recovery in oil producing formations, waterflooding is often implemented by the Operators. This is achieved by drilling injection wells or converting the oil producing wells into injectors. The injection wells are located at carefully selected points in the oilfield so that the water displaces as much oil as possible to the production wells before the water starts to break through. A significant saving in an oilfield development can be obtained by reducing the actual number of injecting wells and increasing each of the injector wells’ capacity for injection. Balancing the injection and produced volumes often involves injecting at high pressures leading to the fracture of the reservoir rocks along a plane intersecting the wellbore. This happens when injection pressure exceeds the minimal principal stress and the tensile strength of the rock, thereby creating a hydraulic fracture. With continuous injection, these fractures start propagating into the reservoir and may reach the reservoir caprock, which may decrease the integrity and possibly lead to out of zone injection. The study of evaluation of downhole fracture monitoring is divided into two parts. In the first part of the paper (Kohli, et al., 2021), a downhole verification approach to identify the fracture initiation point(s) is the focus. It describes the planning, execution and interpretation of the downhole data. This includes spectral acoustic monitoring and modelling of the temperature responses to quantify the injectivity profile. In this second part of the paper, the direct business impact is discussed by further integration of acoustic monitoring and temperature modeling data with detailed results from of fracture dimension (height) measurement by means of pressure fall off tests. Combined, both studies form an integrated approach that the operator took to prove that the fracture network propagation remains within the reservoir and that the top seal integrity is maintained.

Downhole Monitoring of Fractures in a Waterflood Development – Part 1

When an oilfield is exploited by simply producing oil and gas from a number of wells, the reservoir pressure in many circumstances drops quicker than normal impacting the production rates (Koning, 1988) and well performance. To maintain the pressures in the oil producing formations, waterflooding enhancement method is implemented by the Operators. This is achieved by drilling injection wells or converting the oil producing wells into injectors. The injection wells are located at carefully selected points in the oilfield so that the water displaces as much oil as possible to the production wells before the water starts to break through. A significant saving in an oilfield development can be obtained by reducing the actual number of injecting wells and increasing each of the injector wells' capacity for injection. Balancing the injection and produced volumes often involves injecting at high pressures leading to the fracture of the reservoir rocks along a plane intersecting the wellbore. This happens when injection pressure overcomes the rock stress and its tensile strength, thereby creating an induced fracture network. With continuous injection, these fractures start propagating into the reservoir and may reach the reservoir caprock. Continuing to inject further in such a fracture system may breach the top seal integrity of the caprock leading to uncontrolled out of zone injection. The study of evaluation of downhole fracture monitoring is divided into two parts. In this paper a downhole verification approach to identify the fracture initiation point(s) is the focus. It describes the planning, execution and interpretation of the downhole data. This includes spectral acoustic monitoring and modelling of the temperature responses to quantify the injectivity profile. In paper (Kohli, Kelder, Volkov, Castelijns, & van Eijs, 2021), the direct business impact and regulatory requirements are discussed by further integration of acoustic monitoring and temperature modeling data with detailed results from downhole measurements of fracture dimensions by means of pressure fall off tests. Combined, both studies form the integrated approach that the Operator took to meet the regulatory requirements proving that the fracture network propagation remains within the reservoir and that the top seal integrity is maintained.

De-Risking Thermal Induced Sustained Annulus Pressure to Safeguard Optimal Production

Sustained Annulus Pressure (SAP) is a common production constraint in the oil and gas industry, it is usually caused by impaired seal Integrity within the wellbore system resulting in barrier failures. In peculiar scenarios the thermal expansion creates pressure build-up in the annulus as well which can equally impair the integrity of the wellbore. In this paper the results of downhole and surface pressure monitoring surveys are presented, the objectives aim at determination of both downhole leaks and verification the influence of thermal expansion into a wellbore system integrity in a field located onshore Niger Delta. SAP in a producing well was earlier recorded during routine annular pressure monitoring in 2017 during the production rate increase by changing the bean size from 18/64" to 24/64". Initial diagnostics observed pointed towards SAP resulting from a possible downhole seal integrity issue leading to a leak to the surface. While putting the well on stream with current bean size and the pressure regime for both THP and CHP was observed. Pressure with time analysis showed annulus pressure builds up rapidly while flowing and bleeds off within 30 min from 700 psi to 0 psi when well shut in. Downhole logging and sensitive passive acoustic monitoring was conducted, the survey aimed to detect barrier failures by capturing its acoustic leak patterns under shut-in and bleeding off condition. Considering the suspected leak behaviour, the data acquisition included the procedure to build up the annulus pressure by flowing the well and monitoring the annulus discharge. Integrity logs survey and passive acoustic monitoring confirmed there were no downhole failures and after several bleed-offs when Tubing choke was beaned down to 18/64" no annulus pressure build-up was observed from the Well head gauge on the Casing head confirming the source of the sustained annulus pressure is driven by the temperature expansion of the annulus fluid. Remedial action and recommendation after Simulation were to de-risk the well at a controlled bean size to mitigate SAP and optimally flow the well.

Laboratory Evaluation of Mechanical Properties of Draupne Shale Relevant for CO2 Seal Integrity

The mechanical integrity of caprocks overlying injection formations is one of the key factors for safe storage of carbon dioxide in geological formations. Undrained effects caused by CO2 injection on strength and elastic parameters should be properly considered in the operational design to avoid fracture creation, fault reactivation and unwanted surface uplift. This study presents results from eleven undrained triaxial compression tests and one oedometer test on the Draupne shale, which is the main caprock of the Smeaheia site in the North Sea, to extract parameters relevant for seal integrity. Tests have been performed on samples oriented perpendicular to and parallel with the horizontal layering of the rock to study the effects of sample orientation relative to the loading direction. Results from undrained triaxial tests showed only minor effects of sample orientation on friction and cohesion. However, when loading during undrained shearing was parallel with layering (horizontal samples), measured Young’s modulus was roughly 1.4 times higher than for the vertical samples. Undrained shearing of vertical samples generated 30–50% more excess pore pressure than for horizontal samples with similar consolidation stress owing to more volume compaction of vertical samples. With apparent pre-consolidation stress determined from a high-stress oedometer test, the normalized undrained shear strength was found to correlate well with the overconsolidation ratio following the SHANSEP (Stress History and Normalized Soil Engineering Properties) procedure.