Abstract. Retraction spring is a type of orthodontic apparatus that is used to move a tooth with respect to another by utilizing its spring back effect. It is made of metallic wire formed to individual orthodontic cases. A specific geometry results in a set of force system, consisting of forces and moments, that provides specific movement effect when it is pre-activated to the adjacent teeth. Currently, orthodontists select its geometry depending on their knowledge and experience. It is based on separate and less-than-comprehensive literatures that not all orthodontists have access to. It may result in inaccuracies in treating individual tooth retraction case. Engineering approach to estimating retraction spring structural behavior is proposed through analytical, numerical and empirical methods. Castigliano method is used as the analytical approach, whilst finite element method is used as the numerical approach. The two simulation approaches were compared to the experiments to obtain the best simulation model. The behavior of the simulation models agree well with those of experiments. Hence, the simulation models were used to simulate a large number of geometries to form database of structural behavior of retraction spring that could be used in the geometry selection by orthodontists.

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Conventional hydraulic fracture stimulation techniques have been widely used to enhance production from tight gas reservoirs. Since the initial use of this method to increase production rates, the industry has witnessed continued advancement in terms of fracturing theory, fluids, and techniques. The use of carbon dioxide (CO 2 ) since the early 1960s has continued to be a significant part of these advances. CO 2 has been used for many years as an energy source to aid fluid recovery of well stimulation fluids. This technology predominantly has been used to stimulate tight sandstone reservoirs. There are very limited applications for low permeable tight carbonate reservoirs because of complexities associated with the physical and mechanical properties of carbonate rocks and its interaction with fracturing fluid. Nevertheless, the advantages of using assisted CO 2 stimulation fluids as the elimination of potential formation damage normally associated with fracturing fluids and very rapid cleanup are still present.This paper outlines one of the first acid fracturing jobs assisted with CO 2 conducted on a tight gas well reservoir in Saudi Arabia. It describes in a simple manner the screening methodology and key parameters considered during selection of a well candidate and the design process, which was based on petrophysical, mechanical, and chemistry properties of the formation and the respective interaction with treatment fluids. Moreover, primary operational procedures and guidelines are discussed, highlighting a safety risk assessment point of view.Implementing this technique in a more generalized manner in the field can help save considerable operational time and costs. CO 2 used to energized fracturing fluids can increase the productivity of the well while using less water and less acid than conventional acid fracturing, which is of primary importance in such a harsh environment, requiring less water consumption.

fax 01-972-952-9435. AbstractOver a significant time-period, during the development of a field; a number of factors will contribute to an increased understanding and appreciation of the identification of pay, it's distribution and potential. As a result, it is not unusual to find that a significant number of opportunities may exist within existing well-stock; but that these opportunities are 'isolated' by limitations of the original completion design. Accessing these reserves then simply becomes a question of completion 'adaptability', optimization and economics. Therefore this paper describes the application of a rig-less 'cement-packer' approach, in order to economically access these reserves, while retaining the necessary level of completion integrity. The paper describes the steps involved in achieving this, from concept, through planning to execution. Finally, a number of case-studies (with variants) are presented to demonstrate the increasing development and applicability of the process.It is likely that an operator would consider that such by-passed opportunities would generally require a costly, lengthy and complex work-over operation; and potentially discard the option due to the economics and risks. However, this paper clearly demonstrates that the cement-packer approach is a simple, efficient and economic method of accessing such bypassed pay, while helping ensure acceptable well-bore integrity is retained.

Straits of Malacca Exploration Campaign marks PETRONAS' first oil/gas well drilling in the region of West Coast of Peninsular Malaysia. Three (3) exploration wells were drilled in a period of four (4) months. This paper will highlight the challenges, lessons learnt and key to success of this fast track drilling campaign in a new region of operation.The team which was entrusted with the mission to drive PETRONAS' quest of oil and gas in this new region were then given six (6) months to deliver the first well out of three (3) exploration wells. Apart from the uphill task to set up staging base and logistics support in the West Coast of Peninsular Malaysia, the team faced challenges of drilling in one of the world's busiest shipping lane. Navigational safety is one of the main concern here. Besides, two (2) of the three (3) wells were located close area where sea robberies and hijacking were rampant. In terms of drilling operation, two (2) of the wells were exposed to the risk of total losses. This paper will share the approaches taken by the project team in overcoming challenges in three (3) main areas -(1) logistics; (2) navigational and offshore safety and security; and (3) well engineering.Although faced with numerous challenges together with limitation of time and resources, the project team has managed to deliver all the three (3) wells successfully, meeting all the geological objectives within Authorisation For Expenditure (AFE) cost. On top of that, the drilling campaign was completed with zero Lost Time Incident (LTI) and zero accident. Another notable success in this project is setting up the modus operandi in a new region of drilling within six (6) months. Due to the fast track nature of this campaign, first of the three (3) wells was spudded concurrently with 3D seismic interpretation by taking the risk of relying on 2D seismic data. Halfway through the well construction, Well #1 (Well A) was re-sanctioned based on the findings while drilling and latest 3D seismic data received. Target depth of the well was revised to 3130m TVDSS from initial 2100m TVDSS. Despite all the challenges, the drilling team managed to complete drilling operation of three (3) wells ahead of time by 11 days in total.Apart from engineering and logistics challenges, this paper will share the experience of drilling in one of the busiest shipping lanes in the world. Lessons learnt and key success factors of this fast track exploration drilling campaign will be beneficial to all oil and gas (O&G) operators, especially to those planning to operate in the Straits of Malacca or any other similar regions in the world.