An offshore gas field has been producing sand for a few years. Sand production has been closely monitored through acoustic flowline devices and a sand collection system installed on the platforms. Observation of sand production has triggered evaluation of whether to install surface desanders or complete future wells with downhole sand control. This evaluation requires a prediction of sanding rate over the reservoir life. The possibility of providing downhole sand control on existing wells was also evaluated in separate studies. Predicting sanding rate, particularly for gas fields, has been historically challenging, mainly because of the sporadic nature of sand production, inadequate quantification of fundamental physics, and lack of representative lab tests, and reliable field calibration. To tackle these challenges, four studies have been designed and executed, including 1) the development of a reliable log-based rock strength estimate; 2) the prediction of sanding rate over the reservoir life for a conservative well condition; 3) the evaluation of sand particle transport from the reservoir to the surface facilities; and 4) the estimate of potential erosion of platform facilities. The sanding rate prediction is based on extensive laboratory tests of four carefully selected whole cores, with gas and water flow. It has then been validated by field monitoring data from an acoustic flowline device on each producer and a sand collection system on the platforms. The studies have provided a prediction of future sand production, how much of the produced sand will be seen at the surface (and therefore how much of it will fall into the rathole), how fast various components of the surface facility will erode over the field life, and what will be the optimal completion strategy for sand control should it become necessary. They have provided input to an integrated evaluation of completion design, reservoir management, platform configuration, and field economics. Introduction For a long time sand production has been viewed as a cost source and a safety hazard for the oil and gas industry. It can erode downhole equipment and surface facilities, cause pipeline blockage, leakage, damage casing due to formation subsidence, lead to more frequent well intervention and workovers, and generate additional need for sand disposal. Since the 1980s, however, it has been consistently demonstrated that sand production could also be beneficial in both heavy oil reservoirs (Dusseault and Santarelli, 1989) as well as conventional oil reservoirs (Andrew et al., 2005). To allow sand production up to a certain level could result in a large amount of cost savings from the simplification or even elimination of downhole sand control. More importantly the removal of sand from the rock matrix could enhance the near wellbore porosity and permeability, promote oil mobility, and therefore increase production rate (Dusseault and Santarelli, 1989; Han et al., 2007). Economic benefits of avoiding complex and expensive downhole sand control have encouraged many oil and gas operators to select sanding strategies from a comprehensive evaluation of the sanding prediction, the equipment and facility tolerance, and the field CAPEX, OPEX, risk, HSE, etc. (Rawlins and Hewett, 2007), rather than simply reacting to the onset of sanding.

Summary An offshore gas field has been producing sand for a few years. Sand production has been closely monitored through acoustic flowline devices and a sand-collection system installed on the platforms. Observation of sand production has triggered evaluation of whether to install surface desanders or to complete future wells with downhole sand control. This evaluation requires a prediction of sanding rate over the reservoir life. The possibility of providing downhole sand control on existing wells was also evaluated in separate studies. Predicting sanding rate, particularly for gas fields, has been historically challenging, mainly because of the sporadic nature of sand production, inadequate quantification of fundamental physics, and lack of representative laboratory tests and reliable field calibration. To tackle these challenges, four studies have been designed and executed: (1) the development of a reliable log-based rock-strength estimate, (2) the prediction of sanding rate over the reservoir life for a conservative well condition, (3) the evaluation of sand-particle transport from the reservoir to the surface facilities, and (4) the estimate of potential erosion of platform facilities. The sanding-rate prediction is based on extensive laboratory tests of four carefully selected whole cores with gas and water flow. It then has been validated by field-monitoring data from an acoustic flowline device on each producer and a sand-collection system on the platforms. The studies have provided a prediction of (1) future sand production, (2) how much of the produced sand will be seen at the surface (and, therefore, how much of it will fall into the rathole), (3) how fast various components of the surface facility will erode over the field life, and (4) what will be the optimal completion strategy for sand control should it become necessary. They have provided input to an integrated evaluation of completion design, reservoir management, platform configuration, and field economics.

Sand production in oil and gas wells not only poses a serious threat to hydrocarbon production, but can also cause extensive damage to equipment, such as subsurface tubing, surface valves and pipelines. Produced sand is also an environmental hazard, and needs to be disposed of in an environmentally safe way. Effective sand management is therefore a major concern in the oil and gas industry.The key challenge is to optimize hydrocarbon production by minimizing the production of sand and in doing so reduce the damage caused to well completions and surface equipment. On a sand-prone well, this is typically done by identifying a maximum sand free rate (MSFR), and then limiting production to this level. Conventional sand detection methods rely on surface measurements. However, these methods do not provide a complete picture of the sand production down hole. To gain a more comprehensive understanding of the problem, sand needs to be detected at its point of entry into the well bore. In this way, the best remedial treatment can be designed.To answer this requirement, an ultrasonic sand detection tool has been developed. The tool detects ultrasound energy generated by sand grains as they enter the well bore and strike the tool in a radial manner. Sand moving parallel to the well bore axis is not detected, thus the tool can indicate the exact entry point of sand, anywhere along the producing interval. The operator can then specify the most appropriate and cost effective remedial action, such as installing sand screens or applying chemical treatments. By employing such a tool, the cost of remedial action can be minimized and hydrocarbon rates can be optimized to achieve sand-free production. The tool can also be used to evaluate the performance of sand screens and other control devices, and if run in tandem with production logging tools, can monitor sand production in conjunction with well performance. This paper presents the results of a case study where a downhole ultrasonic sand detector was used to monitor sand production in five gas-producing wells from the Northern Malay Basin. The methods behind this "sand survey" are presented, along with a description of the tool.