TITLE: Water Based Drilling Fluid Analysis
EXECUTIVE SUMMARY: Analysis of drilling fluids is essential to their performance. In this laboratory exercise the aim is to test three drilling fluid samples for; density and rheological properties, Fluid loss, chemical analysis i.e. testing pH, alkalinity, testing for chloride ions, calcium carbonate, calcium, bentonite; also determining the amount of solids present in the samples as well as volumes of oil, water and solids contained in the sample, and to test for contaminates such as NaCl and KCl. These tests helps us to determine the properties of the drilling fluid and so what can be done to make the mud perform more efficiently. For the density and rheological properties a mud balance is used to test density i.e. fill the cup so that a little is ejected through the hole at the top and then move the weights until balance is achieved which is indicated by the bubble in the spirit level. The rheological properties are tested at room temperature and heated using a rotational viscometer which has shear rates of 600rpm; 300rpm, 200rpm, 100rpm, 6rpm, 3rpm or “gel” and 10second and 10minute gel can also be found. These rate especially the 600rpm and the 300rpm are then used to calculate PV (deals with the total solids) and YP (deals with the carrying capacity of the mud), the gel is related to the gel strength which deals with the suspended capacity. From analysis when heated as compared to when at room temperature the PV and YP should not vary by much which would be influenced by the values obtained from the different shear rates. The differences for the rheological properties stems from the additives that are used in the sample. For the Fluid Loss comparing the measured value (30mins) with the calculated value (2X 7.5 mins) there should not be a great loss. The fluid loss is done according to API fluid loss using an API LTLP filter press which uses a pressure of 100psig to essentially push the fluid out of the mud thus remaining with only solids and therefore observe the filter cake formed and the properties of the filter whether it is pliable, not-pliable, thick or thin (thick is not good since this can inhibit more fluid loss). In the 30mins it should be seen that sample A losses the lest amount of fluids while Sample C loses the most and Sample B appears closest to the original. The filtrate collected from each sample is then used to conduct chemical analysis which is achieved essentially through chemical reactions derived from titrations with known volumes of acids and other solutions. The pH ranges from 9.0 to 10.0 meaning that the mud is slightly alkaline which could mean that there is calcium or calcium carbonate present. Further testing gives us the amount of chlorides present in the samples (A and B chloride content stems from the tap water used in to make the mud) whilst sample C has a high chloride count due to the additives in the sample. For all the samples the MBT ranges from 5.0 to 7.0; the MBT tells of the absorption of the methylene blue solution by the clays the end-point is achieved when “squiggly” lines appear meaning that there is excess methylene blue. Bentonite is used as a viscosifying agent which helps with the carrying capacity of the mud, therefore it is expected that Samples C would contain the most amount of this chemical. Sand content tell of the volume of true volume of sand in the samples and what may appear as sand but is really CaCO3. The retort analysis used heat to separate the samples into oil (if any), water and solids which is water the drilling fluid is made up of. Sample B had oil and minute amounts of solids (not recorded since were not seen). From the salt analysis (testing for NaCl and KCl) only sample C is expected to contain some KCl which would explain the results obtained for the fluid loss and the rheological properties since KCl causes the particles to disperse and not behave as expected. Therefore analysis of the samples:...
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