First Successful Downhole Sand Detection in Malaysia
Authors: Mustafaal Bakeri Fahmi Amni , Ashqar Ayham , M Shah Jamari , Jamaluddin Junirda , A Karim M Azan 
Published: November 2019

This paper presents the first successful downhole sand detection survey performed using an evolving technology. Sand production from the weak, but competent, reservoirs is a growing concern and may lead to reduction in production. Formations producing sand require special treatments to prevent completion and surface equipment damage.

The Field in discussion is located offshore Malaysia. Reservoirs are composed of fine to very fine sandstone with interbedded silts and clay layers. Field production commenced in 1969.

Spectral Noise Survey was ran to confirm perforated zones contributions, and attempt to detect downhole sand production. Even though noise surveys are designed to identify flowing reservoir intervals, cross-flows, behind casing, tubing and casing leaks, however the use of correct frequency and longer stationary times allows the identification of sand particles moving within the flow. De-sander was rigged up on surface to monitor and confirm sand production. Spectral noise data was acquired across the perforated intervals using specially designed station time and frequency. The well was flowed at two different chock sizes. Downhole sand detection measurements were performed at both.

Spectral noise density in the depth-frequency plane undergoes a wavelet transform. At each measurement depth, several tens of noise signals are recorded. These are analyzed to remove statistically insignificant details from the signal spectrum and to suppress noise components that are present throughout large depth intervals.

Noise data is collected, and analyzed across the four perforated intervals at two different chock sizes. The technology successfully separated solids from fluid signal, which is critical to ensure sand particles are captured. The measurement indicated sand production originates from one perforated sand, the same sand contributed to the majority of production. Surface sand samples were collected and analyzed. These indicated a unimodal grain distribution that are within the tool detection and resolution. The change in choke size confirmed that sand production can be controlled by reducing the production rate. Prediction of maximum sand-free production rate provides information for sand-control decisions and allows maximization of rate in wells that are completed without sand control

The innovative technology delivered an important downhole measurement of sand production. The data significance is when used to calibrate reservoir, and geomechanical models, confirm sand-free rate production, and effectively manage the choke size during production.

This is the first time such survey is performed using the innovative technology to identify sand production downhole, the importance of this new technology is that the well produces commingle so it is critical to assess intervals contribution to the sand production. Currently there is no proven technology to accurately identify, and detect downhole sand producing formations. Reservoirs are assumed to produce sands based on historical knowledge and expected unconfined compressional stress (UCS) value.