Abstract
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.
