Muhammad Wahab

Six Centuries of Upper Indus Basin Streamflow Variability and Its Climatic Drivers

Our understanding of the full range of natural variability in streamflow, including how modern flow compares to the past, is poorly understood for the Upper Indus Basin (UIB) because of short instrumental gauge records. To help address this challenge, we use Hierarchical Bayesian Regression (HBR) with partial pooling to develop six centuries long (1394-2008 C.E.) streamflow reconstructions at three UIB gauges (Doyian, Gilgit, and Kachora), concurrently demonstrating that HBR can be used to reconstruct short records with interspersed missing data. At one gauge (Partab Bridge), with a longer instrumental record (47 years), we develop reconstructions using both Bayesian Regression (BR) and the more conventionally used Principal Components Regression (PCR). The reconstructions produced by PCR and BR at Partab Bridge are nearly identical and yield comparable reconstruction skill statistics, highlighting that the resulting tree-ring reconstruction of streamflow is not dependent on the choice of statistical method. Reconstructions at all four reconstructions indicate flow levels in the 1990s were higher than mean flow for the past six centuries. While streamflow appears most sensitive to accumulated winter (January-March) precipitation and summer (MJJAS) temperature, with warm summers contributing to high flow through increased melt of snow and glaciers, shifts in winter precipitation and summer temperatures cannot explain the anomalously high flow during the 1990s. Regardless, the sensitivity of streamflow to summer temperatures suggests that projected warming may increase streamflow in coming decades, though long-term water risk will additionally depend on changes in snowfall and glacial mass balance.

From Imagination to Reality: Case Study of an Appraisal Well For CO2 Sequestration Project in Malaysia

In Malaysia, more than 70% reserves are held within carbonate reservoir with more than 13TcF of hydrocarbon gas locked in high CO2 fields. With that PETRONAS are embarking journey to unlock and monetize the high CO2 gas fields via CO2 sequestration project with the aim to separate CO2 and store CO2 underground thru pilot project in Field A. Field A is unique in several aspects whereby it has 70% CO2 and 30% of potential hydrocarbon gas sale which is equivalent to approximately 700 million tons of CO2 to be stored and would be the biggest CO2 sequestration project recorded in industrial. The geological storage site will also be within the same field which is located in deep seated aquifer below the producing reservoir. An appraisal well was successfully drilled in Field A with specific well objectives designed to address critical factors identified in CO2 sequestration project ranging from surface to subsurface. The well recorded several key highlights en route, among others, Malaysia’s first cap rock mini fracture test and first water injectivity test in aquifer interval, PETRONAS longest continuous carbonate coring and first cap rock shale core with 98% and 100% core recovery respectively. The cores data is crucial to de-risking initial GIIP and to update current geological model for further evaluation on A5 field as CO2 storage potential sequestration sites