Structural Reservoir Characterization of Akkas Gas Field, Western Iraq: Implications for Hydrocarbon Recovery

Akkas Field is a structural trap with a sandstone reservoir that contains proven gas condensate. The field is a faulted anticline that consists of the Ordovician Khabour Formation. The objective of this research is to use structural reservoir characterization for hydrocarbon recovery. The stratigraphic sequence of the Silurian and older strata was subjected to an uplift that developed a gentle NW-SE trending anticline. The uplifting and folding events developed micro-fractures represented by tension cracks. These microfractures, whether they are outer arc or release fractures, are parallel to the hinge line of the anticline and perpendicular to the bedding planes. The brittle sandstone layers of the reservoir are interbedded with ductile units of shale. The sandstone layers accommodate the formation of micro fractures that play a major role to increase the secondary porosity. The gas and condensate have been stored mainly through the micro fractures. Two types of drilling have been used for experimental gas production, vertical and horizontal. Horizontal drilling was parallel to both hinge line of the anticline and micro fracture surfaces that was conducted and doubled the gas production of the vertical well multiple times. However, if used the third type of drilling, directional, that is perpendicular to the hinge line and parallel to the beddings of both flanks of the anticline gas production will increase more than the horizontal drilling. The directional drilling will become perpendicular to the fracture surfaces and allow the gas and the condensate to flow into the well from all directions. Additionally, it will reduce the effect of both semi – liquid hydrocarbon condensate and vertical sediment barriers.

Case Study of Identifying and Minimizing Formation Damage in Tight Reservoirs Caused by Drilling Fluids in Abu Dhabi Onshore Operation Using Compatibility Coreflood Studies

A study was carried out to examine formation damage mechanisms caused by drilling fluids in tight reservoirs in several onshore oil fields in Abu Dhabi. Three phases of compatibility corefloods were carried out to identify potential to improve hydrocarbon recovery and examine reformulated/alternate drilling muds and treatment fluids. Interpretation was aided by novel Nano-CT quantifications and visualisations. The first phase examined the current drilling muds and showed inconsistent filtrate loss control alongside high levels of permeability alteration. These alterations were caused by retention of drilling mud constituents in the near-wellbore and incomplete clean-up of drilling mud-cakes. Based upon these results, reformulated and alternate drilling muds were examined in Phase 2, and there was a positive impact upon both filtrate loss and permeability, although the Nano-CT quantifications and visualisations showed that drilling mud constituents were still having an impact upon permeability. Candidate treatment fluids were examined in Phase 3, with all having a positive impact and the best performance coming from 15% HCl and an enzyme-based treatment. The interpretative tools showed that these treatments had removed drilling mud-cakes, created wormholes, and bypassed the areas where constituents were retained. The compatibility corefloods on tight reservoir core, alongside high-resolution quantifications and visualisations, therefore identified damaging mechanisms, helped identify potential to improve hydrocarbon recovery, and identify treatment fluid options which could be used in the fields.

Innovative Liner Hanger System Designed for Operational Benefits in Harsh Environments

Since the beginning of drilling for oil, improving efficiency and reducing the cost of hydrocarbon recovery have been key issues when designing a well. Since then, new methods and techniques have developed the industry. One of the most critical events in the oil and gas industry was the invention of the liner hanger. Since Liner Hangers are utilized as the primary solution to wellbore construction, they have been designed with such requirements in mind. This paper will deliver an insight to an innovation life cycle where a stakeholder collaborated together to successfully deliver, plan and complete the first 15,000 PSI, 400 °F high pressure- high temperature (HPHT) Liner Hanger designed to overcome the operational obstacles that conventional liner hangers have when deployed with Multistage Frac (MSF) completion systems but still allows for successful operations in cemented completions. This liner hanger technology has been run in different parts of the world and has proven since the beginning that with all the features included in the designed stages.

An Empirical Analog Benchmarking Workflow to Improve Hydrocarbon Recovery

Summary Benchmarking the recovery factor and production performance of a given reservoir against applicable analogs is a key step in field development optimization and a prerequisite in understanding the necessary actions required to improve hydrocarbon recovery. Existing benchmarking methods are principally structured to solve specific problems in individual situations and, consequently, are difficult to apply widely and consistently. This study presents an alternative empirical analog benchmarking workflow that is based upon systematic analysis of more than 1,600 reservoirs from around the world. This workflow is designed for effective, practical, and repeatable application of analog analysis to all reservoir types, development scenarios, and production challenges. It comprises five key steps: (1) definition of problems and objectives; (2) parameterization of the target reservoir; (3) quantification of resource potential; (4) assessment of production performance; and (5) identification of best practices and lessons learned. Problems of differing nature and for different objectives require different sets of analogs. This workflow advocates starting with a broad set of parameters to find a wide range of analogs for quantification of resource potential, followed by a narrowly defined set of parameters to find relevant analogs for assessment of production performance. During subsequent analysis of the chosen analogs, the focus is on isolating specific critical issues and identifying a smaller number of applicable analogs that more closely match the target reservoir with the aim to document both best practices and lessons learned. This workflow aims to inform decisions by identifying the best-in-class performers and examining in detail what differentiates them. It has been successfully applied to improve hydrocarbon recovery for carbonate, clastic, and basement reservoirs globally. The case studies provided herein demonstrate that this workflow has real-world utility in the identification of upside recovery potential and specific actions that can be taken to optimize production and recovery.

Forecasting Hydrocarbon Production at Gas Condensate Fields Considering Phase Transformations of Reservoir Systems

Based on the results of PVT studies, a methodology for estimating hydrocarbon recovery at various stages of a gas condensate field development, depending on the current weighted average reservoir pressure in the gas drive, is considered. In this case, the physical processes related to the phase transformations of the reservoir gas condensate mixture with a decrease in reservoir pressure in the deposit are assumed identical in the PVT bomb. That is, the effect of the porous medium is neglected. This allows describing the processes of phase transformations with the same equation of material balance, based on which it is possible to forecast hydrocarbon recovery at gas condensate fields, and provide a control over the results of phase transformation modelling of the reservoir gas condensate mixture in phase balance bomb (PVT bomb).

The Use of Controlled Dissolution Glass for the Consolidation of a High Porosity Chalk

This paper reports the development and testing, of a Phosphate controlled dissolution glass composition used to strengthen the matrix of chalk whilst retaining the permeability of the rock, facilitating improved hydrocarbon recovery in unstable wells. Multiple versions of the glass solutions and different types of colloidal silica were extensively tested in the laboratory to determine injectability and reactivity with calcium carbonate rocks. The goal of the testing was to determine the best performing solution for use in a field trial in the Norwegian North Sea. The laboratory testing included filtration and core flood tests to determine the injectability of the solutions and post treatment permeability, and Brazilian strength tests to determine the tensile strength of the treated chalk cores. The filterability was tested through filter screen sizes ranging from 5 to 0.6 µm. Core flood testing was performed on 10 cm long chalk cores with 1.5 mD permeability. The glass solutions showed the best results in the filtration and core flood testing, achieving significantly greater invasion depth than any of the colloidal silica samples. The phosphate glass treated chalk cores maintained 70 to 100% of the original permeability while delivering a 3 to 5 fold tensile strength increase. The lab tests demonstrated the potential of a glass based treatment to strengthen chalk formations without impeding permeability.Based on the promising results from the lab tests, it was decided to trial the selected glass solution in a mature vertical proppant fractured well. The test confirmed that the glass solution could be pumped into the well, but the test failed pre-maturely after two months of varied production, and the trial will not be covered in this paper.However, due to the high value in being able to stabilize chalk in the field, the Operator is evaluating a new trial in a horizontal well, and learnings from the first trial will be used to inform further lab tests in the next phase. The glass solution used in this trial is being further developed to be used in other formation types, such as sand and non-calcium containing reservoirs.

The Use of Tracer Based Dynamic Production Profiling in Estimating Hydrocarbon Recovery in Directional Wells

Production surveillance in the producing wells has been an important task for many years in oil and gas development since it provides relevant information useful for the effective management of the HC production. The main objective pursued by operators is to increase the production volume and enhance the oil recovery rate, which often requires some additional well interventions in the existing producing wells. For this purpose, it is necessary to understand how and where to perform stimulations and properly select adequate EOR technologies in order to avoid the risks associated with premature complications of well operation. Usually, production surveillance can be performed using standard logging methods (PLT complex), aimed at the inflow profile monitoring in a well. There are many factors, however, that may complicate the data recording and affect the reliability of the study results. In addition, it is not always possible to shut down the well for production logging purposes. As an alternative approach, it is proposed to consider a technology that involves the placement of special marker-reporters in the bottom-hole zone of the well [3]. The inflow tracers are gradually washed out in the course of production, thus providing the possibility to directly assess the current flow rate, while different codes of productive intervals enable quantification of the production with a phase-wise analysis (hydrocarbon and water) [5]. This paper presents the results of the analysis of reserves recovery in a multi-layer reservoir characterised by relatively low porosity and permeability parameters by means of a tracer-based technology designed for production profiling in directional wells. Surveillance of each productive interval's performance over time was conducted by taking reservoir fluid samples from the mouth of several wells during stable production without well shut-down.

Enhancing Reservoir Stimulation and Productivity Through Reservoir Tunneling Technologies: A Review on Recent Development

The oil and gas industry has been developing various technologies to increase the productivity and recovery of hydrocarbons from conventional and unconventional reservoirs. Reservoir stimulation is an essential operation used to enhance production in many fields around the world. Hydraulic fracturing and acid treatments are the main stimulation methods. Reservoir tunneling concepts are used to drill branched channels in the formation from the main wellbore. With thousands of tunnels drilled to date, it is a viable technique that can improve the recovery of selected reservoirs. This paper reviews the recent developments in reservoir tunneling technologies and their current applications. These tunneling methods can be categorized mainly into water jetting, abrasive jetting, reactive jetting (acid), and needle and mechanical tunneling (radial drilling). The paper includes reviewing and analyzing these techniques based on documented literature results that include simulation studies, lab and yard experiments, field implementation, candidate selection, operational requirements, technology enhancements, advantages, limitations, and challenges of each technique. The paper provides a comprehensive summary of different tunneling techniques focusing on the operational practices, tunneling mechanisms, tunneling depth, and recent advancements available in the market. The most effective applications of the tunneling techniques are in stimulating low permeability, depleted and thin reservoirs, layers close to water zones, and bypassing near wellbore formation damage. The efficiency of creating tunnels is affected by many factors such as reservoir properties, nozzle, and fluid types, etc. The tunnel shape and trajectory are affected by reservoir geological properties. The combination of the tunneling with other stimulation techniques can result in more effective treatments, which enhance the methods of current stimulation. Reservoir tunneling technologies can pave the way to improve hydrocarbon recovery and enable access to unstimulated formations.