Sand Management in the current oil industry trend is one of the important aspects for operators. Managing sand, be it downhole or at surface depending on economic analysis provides an optimised production with proper risk mitigation. Just like for proper hydrocarbon optimisation, accurate monitoring tools such as well test that uses separator or multiphase flow meters are being used and are evolved. Similarly, sand production monitoring is one of the key components during sand management production. Without a proper and reasonably accurate monitoring of sand being produced, it is not possible to manage. With the advent of various techniques of sand monitoring evolved in the last few decades, the industry is moving further on how to improve the new methods of monitoring or utilising the current techniques more effectively. The industry is still struggling to make significant improvements or find new methods of monitoring or more effective application of the current techniques. analogy between sand management and hydrocarbon production and the significance of the same in sand management.

Field development planning is one of the core business processes in the upstream oil and gas industry. Before a discovered field can be developed and its hydrocarbon produced, proper evaluation and planning of the subsurface reservoirs and surface facilities are necessary to ensure that the field development plan is not only economical to undertake, but also flexible enough to cater for any deviation from the original plan during implementation as a result of inherent uncertainties in the reservoirs over the production life span of the field. This paper describes the approach taken to prepare a Field Development Plan (FDP) for a cluster of gas fields located offshore Peninsular Malaysia. The four gas fields namely Melor, Laho, Tangga and Tangga Barat ("Tangga Barat Cluster" in short) are located within a 25 km radius of each other at a common centre. One common denominator among these fields is the presence of carbon dioxide (CO2) in its reservoirs. The Tangga Barat Cluster fields will be developed with Tangga Barat as the central processing complex, designed for a peak capacity of 440 MMscf/d of raw gas with an initial blended CO2 level of 37 mol % prior to CO2 removal. The raw gas will be processed, pre-treated and CO2 content reduced to below 8 mol % for evacuation to Peninsular Malaysia via an existing infrastructure. The key areas emphasized in the preparation of the field development plan include the business driver, resource assessment, depletion strategy, development concept and selection, managing uncertainties, appraisal requirements, reservoir management, anticipating production problems and disposal of the excess CO2. Introduction The Tangga Barat Cluster fields are located about 150 to 170 km northeast of Kertih, Terengganu offshore Peninsular Malaysia (Figure 1). The Tangga Barat Cluster consists of four gas fields; Melor, Laho, Tangga and Tangga Barat. In the vicinity are two producing fields, Resak which is a gas development located about 51 km southwest of the Tangga Barat field and Dulang, an oil development situated about 20 km south of Tangga Barat. The Tangga Barat Cluster fields were discovered from 1980 to 1993; they remain undeveloped due to the presence of CO2 in its reservoirs, the content level of which is beyond the gas specification required for gas sales. Since then, a total of 10 exploration and appraisal wells have been drilled before the final FDP was submitted and approved by PETRONAS, the host authority for upstream oil and gas business in Malaysia.

Sand Production is a challenge in the oil and gas (O&G) production and this was aggravated in last decade due to depleting reservoir pressure. Malaysian brown oil fields have been in production for the last 30-40 years and are reaching their maturity. This leads to low oil production with alarmingsand counts. As a rule of thumb, the production rate would be limited to flow beyond at sand count not more than 15 pptb. As a result, few thousand barrels are locked in within the field due to this limitation and lack of efficient sand separating mechanism at the surface. The emphasis on sand management had always been on controlling the production of the sand by means of utilising various ways of active sand control methods available in the market. Typically, a producing field requires two (2) major discipline sub-surface and surface, with appropriate technical expertise to manage the operation during the life of the field. Surface Sand Management is a newly developed process and engineered system made to handle maximum amount of sand at surface by both theoretical and practical studies for sand removal capability of the existing surface system which can increase production from the well. The concept is a combination of production optimisation and risk handling ability considering all the safety and thereby defining sand limit of a platform or a Pad rather than the complete field. This includes erosion limits (from erosion rate simulation), platform sand handling capacity (desander), procedures and guidelines for sampling, calibrated sand monitoring devices and transportation modelling. Currently, static wellhead de-sander is a solution, but installed on a few wellheads with limited performance due to changes in flow regime and feed quality. Moreover, the excess pressure drop across the well head compromised well deliverability. For gas lifted wells, static well head de-sanders become obsolete when the flow conditions changed from initial design, such as different flow rates or start of slugging effect. A pilot trial of a two-stage centrifugal motorised desander also known as Dynamic Desander was proposed to overcome this challenges and a pilot was conducted in offshore platform to prove the concept. The motor driven desander provided minimal pressure drop and the accumulator at the bottom facilitated large quantity of sand separation. The continuous weigh measurement of separated sand at the outlet can be utilised to monitor the removal efficiency of the desander. The pilot trial was conducted with total of three (3) wells flowing at flow rates ranging from 500 to 1500 blpd. A separation efficiency of 80% up to 99.9% was observed with a total of 2.54T of sand separated in four days of pilot duration compared to 21 days planned earlier. Pilot trial highlighted few limitations of Dynamic Desander technology like inefficient gas handling system, malfunctioned weight indicator especially during high gas inflow and overflow of large particles into the system especially with the inflow of high concentration of sand. Considering the uniqueness of technology, these limitations can be removed by the new design with certain manufacturing changes. Dynamic Desander is a new technology and the pilot was deemed successful which able to identify a better alternative of sand separation solution compared to conventional static de-sander especially for gas lifted environment. In addition, applicable to various feed quality and well rate ranges as well as efficient sand disposal quantification. The Company is looking forward to have another trial on this Dynamic Desander after required modifications in the existing design is fulfilled.

Material balance analysis, a primary engineering technique, is an indispensable tool used for understanding the production performance and field management of mature gas reservoirs. Compilation and analysis of pressure-production data together with acomprehensive geological understanding including in-place hydrocarbon volumes and inter-block communication are prerequisites for material balance analysis. Deviation of observed P/Z data away from a straight idealised line necessitates further study, as it often indicates erroneous estimates of participating in-place volumes, aquifer support or reserves. Lack of pressure measurements, questionable stratigraphic correlations and uncertainty surrounding aquifer propertiesor reservoir connectivity highlight the requirement for further evaluation. The objective of study is to develop a multi-tank material balance modelfor a mature, heterogeneous and compartmentalised carbonate gas field. Ultimately, the model must besufficiently robust to elucidate the field's production mechanism and optimise future field-development opportunities. In this field, the pressure production behavior can be divided into two trends, an early rapid declining pressure trend, followed by a stabilised gradual pressure decline. Owing to higher drawdown in the field's early production life and insufficient recharging, the quick pressure decline underestimates the initial in-place gas volume. This volume is not adequate to support the sustained gas production rates observed in later years. This observation required further detailed analysis regarding the nature of zonal communication across adjacent reservoir intervals to better understand the production behavior of development wells during the design of the material balance model. This paper discusses a study in which material balance analysis is coupled with multi-field network models. Implementation of this workflow can be usedto drive subsurface developmentsin a relatively short period.

Sand Management refers to management of sand from its onset downhole till the handling of produced sand in the top side followed by the disposal while continuously taking safety aspects into account. It is apparent that a single discipline cannot execute this methodology as it requires a multi-disciplinary processed approach to safely produce, handle and dispose the sand. Moreover, for an operator managing multiple assets and each asset having similar issues, it is difficult to work in silos and this also increase the redundancy in tackling the issues. Furthermore, with increase in sand issues all across the regions, ad-hoc solutions became prevalent consuming more money and time. To overcome the challenge of managing the produced and handled sand in an effective and systematic way, initiative was taken by the Operator to formulize the Central Sand Team (CST) involving various disciplines to centralize the entire effort. The objective was to avoid redundancy, standardize the efforts and efficient knowledge sharing. Each region further developed their own Regional Sand Team (RST) with representatives from each discipline. This team will then appoint a Sand Focal Points that will act as the liaison between CST and the RST. Roles and responsibilities were demarcated to both the CST and RST. The Central Sand Team (CST) focus is more on planning the strategy, developing guidelines or procedures, encourage knowledge sharing, being the centralized contract holder for few services and maintaining effective communication with regions' Sand Focal Points. Regional Sand Team (RST), on the other hand are the ones implementing the guidelines & documents and focus on sand related issues & mitigation more apparent in their own region. The holistic approach of assimilating the entire sub-surface and surface disciplines under one umbrella to manage the sand proved effective in reducing the redundancy and coming up with effective solutions. The methodology has also proved a good knowledge transfer tool across disciplines. The sand issue which was usually tackled by individual disciplines is now being tackled collectively with proper data and complete understanding of the sand cycle. The development of Integrated Sand Management Guidelines covers surface and sub-surface aspects. This is a unique concept resulted in a robust and comprehensive document. In addition to that, the sand erosion and transport softwarer is being developed as an application for sand erosion calculations and risk analysis. The methodology in itself is unique and can be blue print for many other operators with sanding issues.