Nur Islami

Time lapse chemical fertilizer monitoring in agriculture sandy soil

Geoelectrical resistivity, hydrogeochemical and soil properties analysis methods were used for chemical fertilizer monitoring in sandy soil at a palm oil plantation in Machang, Malaysia. The time lapse monitoring was done using these methods five times within a three-month period. The hydrogeochemical analysis was conducted over three auger holes to a depth of 1 m and sampled at 25 cm intervals. Chemical fertilizer was applied to the 21 × 21 m2 area after the first data set measurement. The areas outside of this fertilized zone are considered a nonfertilized zone. The other four data sets were acquired at about equal time intervals, thus giving a four-post fertilization data set. The hydrogeochemical measurements indicate that the cations content are relatively similar for every time lapse measurement. However, relatively higher changes of anions content occur at the surface level to a depth of 1 m. The nitrate concentration above the limit for safe human consumption as it returns to the initial value about 100 days after fertilization. The geoelectrical model prior to fertilization showed similar resistivity values at near surface to a depth of about 75 cm with no significant occurrences of low resistivity values. Lower resistivity values were obtained during the second, third, fourth and fifth measurements within the chemically fertilized zone. In the last measurement, the resistivity values in the fertilized zone are almost similar to the nonfertilized zone. This indicates that the contaminant has dissolved into the surrounding environment within this time period.

Permian ultrafelsic A-type granite from Besar Islands group, Johor, peninsular Malaysia

The granitic rocks of the peninsula have traditionally been divided into two provinces, i.e., Western and Eastern provinces, corresponding to S- and I-type granite respectively. The Western Province granite is characterised by megacrystic and coarse-grained biotite, tin-mineralised, continental collision granite, whereas, the Eastern Province granite is bimodal I-type dominated by granodiorite and associated gabbroic of arc type granite. This paper reports the occurrence of an A-type granite from peninsular Malaysia. The rocks occur in the Besar, Tengah, and Hujung islands located in the southeastern part of the peninsula. The granite is highly felsic with SiO2 ranging from 75.70% to 77.90% (differentiation index = 94.2–97.04). It is weakly peraluminous (average ACNK =1.02), has normative hypersthene (0.09–2.19%) and high alkali content (8.32–8.60%). The granites have many A-type characteristics, among them are shallow level of emplacement, high Ga, FeT/MgO and low P, Sr, Ti, CaO and Nb. Calculated zircon saturation temperatures for the Besar magma ranging from 793 ∘ to 806 ∘C is consistent with high temperature partial melting of a felsic infracrustal source which is taken as one of the mechanisms to produce A-type magma. The occurrence of the A-type granite can be related to the extensional back arc basin in the Indo-China terrane during the earliest Permian.

Using time-lapse 4D seismic to monitor saturation changes in carbonate reservoirs

In the past ten years, time-lapse (4D) seismic has evolved as a standard way of monitoring reservoir performance. The method is now being used as good reservoir management practice to provide evidence of saturation changes within the reservoir at field scale. 4D provides a new piece of data describing the dynamic behavior of the reservoir fluids between the wells, often limited to small scale monitoring at the borehole scale. Thus, it provides sophisticated techniques for reservoir monitoring and management relying on the integration of geological models, static and dynamic properties of the reservoir rock, and detailed production and pressure field data.While 4D seismic data has been very successful in monitoring hydrocarbon production from clastic reservoirs, this work has focused on implementing 4D time lapse to monitor saturation changes in carbonate reservoirs and it’s capability to be used as enhanced oil recovery (EOR) tool that can help in enhancing the recovery factor for the filed and help to locate new drilling to sweep more oil out of the reservoir and locate the by-pass oil.The principal goal of this research was to detect the maximum change in seismic attributes (amplitude, acoustic impedance, travel time) that could occur as a result of oil production, water and gas injection in carbonate reservoirs by using time-lapse 4D seismic.

Electrical resistivity imaging and hydrochemical analysis for groundwater investigation in Kuala Langat, Malaysia

ABSTRACT Integrated two-dimensional electrical resistivity imaging (ERI) and hydrochemical surveys were used to investigate the groundwater alluvial aquifer in Kuala Langat, Malaysia. The study in the Langat basin considered the thickness of the aquifer, the depth of the bedrock, the regions influenced by seawater intrusion, and the monitoring of water levels. The resistivity imaging results show that the upper layer consists of clay, while the second layer is an aquifer whose thickness varies mostly in the range of 10–30 m, and in some cases extends to 40 m. The bedrock depth varies from 30 to 65 m. The chemical analyses were carried out on groundwater samples from nine boreholes collected between 2008 and 2012. The analyses indicate that the total dissolved solids (TDS) exceed 1000 mg L-1 near the coastal area and are often less than 500 mg L-1 further inland. The ERI and hydrochemical analyses reveal that groundwater in the study area, especially towards the coast, is a mixture of brackish and fresh waters. EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR M.D. Fidelibus