Review of studies on plugging compositions creation with controlled rheological properties and the ability to restore fluidity for completion, workover and abandonment of oil and gas wells

The main purpose of cementing oil and gas wells is zonal isolation of the formations exposed by the wellbore. During the entire life of the well, there should be no uncontrolled hydraulic communication between the developed formations and the surface, regardless of the composition and type of fluid (water, oil or gas). During the operation of the well, in addition to constant static ones, the casing and cement stone also experience various dynamic loads. The article presents an up-to-date review of experimental studies on the modification of grouting compositions and cement composites capable of autonomous selfhealing due to the introduction of various additives and nanomaterials. Such modification technologies significantly increase the tightness and resistance of cement to the effects of dynamic loads, the integrity of the cement stone. As a replacement for traditional cement materials, the authors propose the creation of grouting compositions with controlled physical and mechanical properties and the possibility of their re-liquefaction under the influence of temperature on the basis of bitumen or bitumen composites. Keywords: well plugging and abandoning; self-healing materials; autonomous self-healing; casing durability; impermeability of the cement stone; self-healing cement; bitumen and bitumen composites.

An Eco-Friendly and Low Carbon Footprint Water Treatment Technology for Produced Water Recycling

Many challenges and limitations are experienced while treating the produced water in oil fields, due to large volumes of water produced together with oil. In this paper, we propose a new method to treat produced water, by integrating humidification and de-humidification desalination (HDH) unit with waste heat, extracted from abandoned oil and gas wells. This solution is based on circulating the produced water through abandoned wells (both vertical and horizontal wells) and heat them up to 60-80°C so that the heated water can be directly used as hot feed water into the HDH unit. This eliminates either electricity or power requirements from an external source thereby significantly lowering the energy requirements. The direct use of hot produced water at the desired temperature range allows for better performance of the HDH desalination unit, while reducing the operating cost, besides minimizing CO2 emissions to the environment. The use of heat extracted from abandoned oil and gas wells in the form of geothermal energy enables the utilization of waste heat associated with existing wells, which is already available in most of the oil fields. The proposed method therefore provides a sustainable renewable energy solution for produced water desalination using HDH processes.

Geothermal Production from Existing Oil and Gas Wells: A Sustainable Repurposing Model

The geothermal energy industry has never quite realized its true potential despite the seemingly magical promise of nonstop, 24/7 renewable energy sitting just below the surface of the Earth. In this paper, we discuss an integrated cloud-based workflow aimed at evaluating the cost-effectiveness of adopting geothermal production in low to medium enthalpy systems by either repurposing existing oil and gas wells or by co-producing thermal and fossil energy. The workflow introduces an automated and intrinsically secure decision-making process to convert mature oil and gas wells into geothermal wells, enabling both operational and financial assessment of the conversion process, whether partial or complete. The proposed workflow focuses on the reliability and transparency of fully automated technical processes for the geological, hydrodynamic, and mechanical configuration of the production system to ensure the financial success of the conversion project, in terms of heat production potential and cost of development. The decision-making portion of the workflow comprises the technical, social, environmental factors driving the return on investment for the total or partial conversion of wells to geothermal production. These components are evaluated using artificial intelligence (AI) algorithms that reduce bias in the decision-making process. The automated workflow involves assessment of the following: Heat Potential: A data-driven model to determine the geothermal heat potential using geological conditions from basin modeling and data from offset wells.Flow Modeling: An ultra-fast, physics-based modeling approach to determine pressure and temperature changes along wellbores to model fluid flow potential, thermal flux, and injection operations.Mechanical Integrity: Casing and completions integrity and configuration are embedded in the process for flow rates modeling.Environmental, Social, and Governance (ESG): A decision modeling framework is setup to ensure the transparent validation of the technical components and ESG factors, including potential for water pollution, carbon emissions, and social factors such as induced seismicity and ambient noise levels The assurance of key ESG metrics will ensure a viable and sustainable transition into a globally available low-carbon source of energy such as geothermal. Our novel cloud- based automated decision-making environment incorporates a blockchain framework to ensure transparency of technical-related processes and tasks, driving the financial success of the conversion project. Ultimately, our automated workflow is designed to encourage and support the widespread adoption of low-carbon energy in the oil and gas industry.

Effect of Nanocellulose in Cement Systems

Cellulose, the one of the most abundant biomaterials available in nature, is a polymer with cellobiose as the smallest repeating unit, with a degree of polymerization that can go up to 1000 for wood cellulose. The strength-to-weight ratio of nanocellulose is eight times greater than steel (Patchiya Phanthong et al). Nanocellulose in suspension (NCS) at a varied concentration helps increase properties of cement without changing the density of the cement slurry. Being mindful of challenges in oil and gas wells, efforts were made to enhance cement properties using nanocellulose within conventional and water-extended cement systems. Samples of 15.8-ppg conventional and 12 ppg water-extended cements were prepared by varying the proportion of nanocellulose within an aqueous suspension. Rheology, sedimentation, compressive strength and mechanical properties were analyzed for a conventional 15.8-ppg cement system with varying NCS proportions of 0, 2, 4, and 5% by weight of cement (BWOC). Similar work was performed for a 12 ppg water-extended cement system by varying NCS differently in proportions of 0, 5, 10, and 20% BWOC. Two-inch cubes were set at 170°F for 24 hours for each sample. They were crushed using hydraulic crush compressive strength equipment, and the force used to break the sample was recorded. Compressive strength for this cement system was measured to be 2450, 3250, 3450, and 3875 psi, respectively, for samples with 0, 2, 4, and 5% BWOC concentrations of NCS. An increase in the strength of cement with an increase in NCS percentage was observed for the 15.8-ppg slurry design, which may be attributed to the size and shape of the NCS. However, similar study carried out with 12 ppg water extended slurries showed decrease in overall compressive strength. Nano-sized particles fill the pores within the sample, impacting structural network development. Additionally, cellulose, having a fiber-like structure, may provide inter-particulate reinforcement. Based on the results of the 15.8-ppg cement system and the high tensile strength of nanocellulose, it can be determined that NCS has a positive effect for increasing mechanical properties. By applying nanocellulose, a tailored cement system (dependable barrier) can be designed to minimize risk and maximize production from oil and gas wells. Nanocellulose is of increasing interest for a range of applications relevant to the fields of material science and biomedical engineering because of its renewable nature, anisotropic shape, excellent mechanical properties, good biocompatibility, tailorable surface chemistry, and interesting optical properties. Low-volume NCS additions can alter the structure of the cured cement system and increase its mechanical properties. This reinforcing mechanism may provide a new opportunity for achieving higher strength cementitious materials.

Indonesia Well Abandonment Standard Gap Analysis; A Review and Suggestion

The old oil and gas wells of approximately 70% are found to have no economic value in Indonesia, leading to being abandoned during the end of their lifecycle, as ruled by the government. This is part of decommissioning an entire field with an environmental preservation program, known as an Abandonment and Site Restoration (ASR). The program involves the evaluation of international permanent abandonment standards, as references for the designs, comparisons, and assessments of Indonesia’s policies. It also provides contrast gap analysis and suggestions in ensuring a proper permanent plug and abandonment approach, to avoid any future leaks or re-abandonment operations. Therefore, this study aims to determine and evaluate the gap analysis between Indonesia and International Well Abandonment Standards, as well as OGUK and NORSOK D-010. The results showed that abandonment activities had improvement opportunities philosophy, and practice, used for plugging/isolations, control lines, as well as reservoir and annular barriers. In addition, literature studies were performed to understand the abandonment philosophy for all reviewed standards, to provide proper suggestions or improvements.

Mechanical and Structural Behavior of Swelling Elastomers under Compressive Loading

Swelling elastomers are a new breed of advanced polymers, and found increasing use in drilling of difficult oil and gas wells. It is important to know how an elastomer will behave under a given set of well conditions, especially after the initial quick-swell period. Good design depends on appropriate material selection. Results are presented in this chapter from experimental and numerical studies conducted to analyze how compressive and bulk behavior of actual oilfield elastomers changes due to swelling. Six key attributes of swelling elastomers needed for design improvement and performance analysis of elastomer seals are discussed: four mechanical properties (elastic modulus E, bulk modulus K, shear modulus G, and Poisson’s ratio ν), and two polymer structure characteristics (cross-link chain density NC, and average molecular weight MC). These parameters were experimentally determined before and after various stages of swelling for two different swelling elastomers being currently used by the regional petroleum industry, in low and high salinity brines. To strengthen the experimental results, and to be able to forecast for other elastomer materials and well conditions, tests were also simulated using the commercial FEM package ABAQUS, using the best available hyperelastic material models.