This paper is to represent reviews of low dosage hydrate inhibitor's (LDHI) evolution and advances, and to provide a general guide for LDHI considerations, historically, hydrate risk has been managed by keeping the fluids warm, removing water, and/or by injecting thermodynamic hydrate inhibitors (THI), commonly methanol or glycol. THIs require high dosage rate therefore production systems can reach a treatment limited by supply, storage, and umbilical injection constraints. Besides, high dosage of MeOH can cause crude contamination for downstream refineries, which may result in penalty. Over last two decades LDHIs have been extensively researched and developed as an alternative hydrate management chemical for oil and gas industry. LDHIs are divided into two main categories; Kinetic Hydrate Inhibitor (KHI) and Anti-Agglomerant (AA), both have been successfully used in field applications, but each comes with their unique challenges for applications, OPEX and CAPEX considerations. LDHIs have proven track records in numerous fields in their performance, either as stand-alone chemical treatment or reducing amounts of methanol/glycol usage, which has directly resulted in CAPEX and OPEX reduction. LDHIs have been instrumental in managing risks of early water breakthrough, high cost of THI storage and transportation, HSSE concerns around THI handling, and undersized pump capacity for required chemical volumes. Switching to LDHIs also offers an economic advantage by reducing umbilical line diameter. Latest advances in the LDHI technology is breaking barriers and pushing limits. The paper summarizes historical advancements in LDHIs over the last two decades, discusses application advantages and limitations, and the criterions to consider for selecting LDHIs.

For the past decade, technology innovation and application have helped to significantly reduce the cost of exploring and producing oil and gas, proving the value technology can bring to the industry. Now while more discoveries are found in ultra deepwater, there is a push to lower CAPEX and OPEX while continuing to produce. This challenge, for both operators and suppliers, compels collaboration and cooperation for improving reliable and innovative technologies including: − Flow assurance technology − Subsea processing − Floating structures − Flowline and pipeline − Risers and umbilicals This paper summarizes some of the results of several recent JIPs on ultra deepwater field development technologies. A review of emerging and existing technologies for deepwater development is presented, which would be of particular interest to technology development personnel and asset team personnel who are in the appraisal or concept selection stages of a project.

Application of dry tree top-tensioned riser systems provides direct vertical access to reservoir via production risers and surface trees, wellbore access for artificial lift and wireline and coiled tubing. While the dry tree riser is gaining growingly attention for deepwater development, the challenge has raised for flow assurance engineering, mainly for the thermal analysis of the dry tree riser - a complex heat transfer system. This paper focuses on the mechanisms of heat transfer in dual and single casing dry tree riser systems. The dry tree riser is a complex system and the heat transfer through the multiple wall of dry tree riser is a complicated process. Current understanding of such heat transfer mechanism is far from satisfactory, often resulting in a large deviation between the predicted and actual system thermal behavior, and temperature profiles or trends. To compensate this, the industry often applies a large safety factor for the system design. This paper reviews dry tree riser related heat transfer study and research in the industries and academics analysis, and provides the state-of-the-art of heat transfer analysis methods for dry tree riser to offshore system engineering and flow assurance, to improve predictions of riser thermal performance at system design phase and for steady state and transient production operation. Introduction Dry tree top-tensioned riser (TTR) systems provide remarkable benefits for deepwater field development such as efficient drilling and major workover access, valve and choke access, wireline logging and coiled tubing access. The system also provides efficient production by allowing no commingling of well fluids, therefore can reduce production downtime and allow higher production rates. The inner and outer annuluses of the dry tree production systems are often filled with N2, inhibited clear-brine fluid, or gel type thermal insulated packer fluid. Due to the extremely large height to gap ratio (H/d), secondary flow or vortices are induced by the buoyancy along the gap, causing an enhanced internal natural convection heat transfer coefficient, thereby an increased overall heat transfer coefficient and heat loss. Currently, there are limited literatures in the industry directly related to the heat transfer through the TTR, either on steady state or transient [1,2], while abundant literatures may be found in the academia and other industries that can be utilized for TTR [3-12]. This paper reviews and study the heat transfer researches that are relevant to TTR. The intension is to provide the stateof- the-art of heat transfer analysis methods and the recommended practices for dry tree riser to offshore engineering and flow assurance. Characteristics of Top-Tensioned Risers A TTR primarily consists of pressure barrier conduit, i.e., production tubing, and environmental barrier conduit, i.e., casing or casings. Depending on workover philosophies and limiting top tension capabilities, the TTR may be single casing or dual casing configurations, as shown in Figures 1 and 2, respectively. In deepwater producing wells the bottom-hole temperature is much higher than the production flowing temperature at the surface, while the temperature of the fluid is much higher than the surroundings.

The Ostra field, developed as part of the Parque das Conchas project, located in the deepwater BC-10 block offshore Brazil, is a relatively low-pressure reservoir. To enable production, an innovative technology of subsea separation and boosting has been deployed. The system consists of manifolded subsea separators with ESPs. Separated liquids are boosted by means of ESP's and transported to the FPSO via an "oil" flowline while separated gas flows to the FPSO via a dedicated gas flowline.A significant risk to the gas flowline is liquid carry-over (LCO) due to potential inefficient separation from the subsea separators -resulting in liquid loading of the gas flowline and associated slugging. This paper addresses the design envelope, operating strategies and liquid management methodologies that will be used to manage the risk associated with LCO into the gas flowline.

Parque das Conchas (BC-10) is a deepwater development offshore Brazil. A novel Caisson / Electrical Submersible Pump (ESP) subsea separator (gas/liquid) and pumping system to enhance production and maximize recovery has been utilized as part of the development of two of the fields (Ostra and Abalone). A third field, Argonauta B-West utilizes multiphase boosting with a modified Caisson/ESP (C-ESP) system to operate with a single, non-separated multiphase outlet. These novel designs have significantly impacted system and flow assurance engineering such as separator level control, hydrate mitigation, system operability, and chemical injection. The fields have been successfully started up with production through the subsea processing system since late 2009. This paper outlines the performance of the subsea processing and production system from the perspective of flow assurance, and presents comparisons of the actual operating performance to design expectations. Learnings from key factors that strongly impact the production system operability and operational strategies are discussed, including the achieved separation efficiency of the caisson, the impact of defoamer performance on caisson operation and the importance of the hot oil circulation system.