Amidst increasing global warming concerns, carbon dioxide, being a major Greenhouse Gas (GHG), poses a threat to the environment if its amount in the atmosphere increases substantially. In this context, carbon dioxide sequestration has emerged as a key technology pathway to reducing GHG emissions. Sequestration is the long term isolation of carbon dioxide from the atmosphere through physical, chemical, biological, or engineered processes. The very nature of the sequestration process involves dealingwith a gas as hazardous as CO2, capable of polluting air, water and land. Hence, health, safety and environment considerations need to be carefully examined at every stage of the sequestration project; right from design to implementation. Major risks involved with a sequestration project are the chance of leakage of sequestered CO2 as well as the risk of fracturing subsurface formations wherein CO2 might be injected. These risks should therefore be strictly maintained in the As Low As Reasonably Practicable (ALARP) region. Safe gas storage, transport, compression, injection and monitoring facilities need to be designed and reviewed regularly. The aim of this paper is to review all the current Health Safety & Environment (HSE) practices, risk analyses as well as HAZOP/HAZID studies being conducted and followed for the implementationof sequestration projects worldwide. The binding laws and policies aimed at safe implementation of sequestration projects are also presented. New methodologies that are being employed for the monitoringof sequestered CO2 gas are also discussed along with possible reasons for their success. Also, previous actual CO2 leakages are presented, along with the damages they caused to the ecosphere of the concerned region. This, being a review paper, the safe practices needed to be implemented for sequestration projectsare highlighted and the state of the art for the same is presented in a consolidated manner.

The Mangala oil field, discovered in 2004 is one of the largest onshore oilfields in India. The field is divided into five reservoir units and contains approximately 1.3 billion barrels of STOOIP. The field currently produces around 175,000 BOPD. The oil is highly viscous, with high paraffinic content, a high pour point, high Wax Appearance Temperature (WAT), as well as high wax dissolution temperature. In addition, high CO2 content, sand production and a high water cut are some of the other notable problems. Keeping this in mind, a combination of innovative technologies had been envisaged right from the development and appraisal stage of the field. The technologies used have been reviewed from a flow-assurance point of view and possible reasons for the selection of these techniques over other methods are also investigated and presented.The waterfloods, EOR pilots, artificial lift systems as well as surface facilities have been designed and implemented keeping in mind the nature of the crude. From a flow assurance point of view, techniques such as hot water injection, coiled tubing heater string, jet pumps etc. have been used extensively. A 670 km long pipeline has been laid from the field to Bhogat in Gujarat for transporting the crude. This pipeline is the world's longest independent heated section pipeline and makes use of another innovation called Skin Effect Heat Management System (SEHMS). A careful examination of these techniques can help us gauge whether they can be put to use to handle similar crudes in other parts of the world. This being a review paper, the working methodologies of flow assurance techniques used for the Mangala crude and the reasons for their success are studied. The Mangala Field and the Mangala crudeThe Mangala field, located in the Barmer basin was discovered in 2004 and is estimated to have around 1.3 Billion barrels of Stock Tank Oil in Place. It is one of the most prolific oil fields of India. There are 5 reservoir units, with the Upper formation dominated by sinuous, meandering, fluvial channel sands and the Lower formation consisting of well-connected sheetflood and braided channel sands. The five units have been named FM1-FM5 from the top down.The sand properties are excellent, with porosities in the range of 21-28% and an average permeability of ~5 Darcy. Fig. 1 shows the Barmer Basin.The Mangala structure is a simple tilted fault block dipping at ~9° to the southeast. Fig. 2 shows the major faults. This structural interpretation is based on a 3-D pre-stack time migrated (PSTM) seismic volume and well data. The structural crest is at ~600mSS and the oil-water contact at ~960mSS. This gives a total oil column of ~360mSS.The Mangala crude is a waxy, sweet crude with an average API gravity of 27°, an in-situ oil viscosity of 9-22cp and live oil wax appearance temperature (WAT) ~6°C lower than average reservoir temperature of 65°C. Another major point that influences all aspects of process design is the high pour point of 40-45°C. The wax dissolution temperature (WDT) of this crud...