Utilizing A Dual Use Local Materials Instead of Imported Foreign Materials for Drilling Mud Conditioning

The most important constituents of drilling operation success is keeping the drilling fluid rheological properties within a certain limit to maintain continuity of their functions in a good manner. To achieve that, the drilling mud system needs continuous and direct supervision such as measuring its rheological properties and treating any deviation in their values. Viscosity is the most important property in hydraulic program success due to its direct relation with a bottom hole cleaning during well drilling, thus related with the drilling rate, so this property should be kept essentially to ensure bottom hole cleaning and high drilling rate at the same time. Some chemicals should be added to the mud system to keep both viscosity and other properties within certain standards and the required limit ,the high cost of such chemicals increase both the metric cost and the final cost of such wells. The aim of this research is to test the physical and chemical properties of a local material, as a thinner and a filtration rate reducer, which tends to decrease the rheological properties of drilling mud. Twenty six samples of different types of drilling mud are tested with both the local and imported foreign materials. The results for both additive materials are compared and it is found that the local thinner has the same trend as the foreign material to a certain extent. Also, in this work, the ideal rheological model is detected among six rheological models by preparing an excel system program to determine the Average Absolute Percentage Error (AAPE). This program compares the calculated shear stress values and the measured values obtained from high pressure high temperature viscometer. The selected models are Bingham plastic model, Power law model, Modified power law model, Robertson stiff model, and Modified Robertson stiff model and Casson model. No.20 Journal of Petroleum Research & Studies (JPR&S) 195 The results show that the Power law and Casson models coincide with the tested samples.


1-Introduction
When recommending a drilling fluid system it must keep in mind that the mud properties must be capable of maintaining the essential functions and at the same time of minimizing both the cost and the expected problems in the well. However, choosing a drilling fluid system must be based on general experience and on the experience gained on site to achieve all the best available technology.
Usually, when functions drop, the mud engineer always requires a change in the conditions and handling to maintain the optimum drilling conditions .A high viscosity mud will undoubtedly improve cleaning of the well, but it will also increase pressure losses and the retention of cuttings. An expert mud engineer knows how to handle these changes and hence how to improve a given function and minimize the resulting impact of other functions on the mud properties. [1] Drilling fluids technology has developed as a significant economic contribution to the production of oil and gas in most countries .Both the introduction of new product for drilling fluids and the development of better practices in their application have come about because there were problems to be solved. Such problems as how to reduce waste of natural resources, how to improve safety in drilling and how to lower costs through time and materials savings have led to the recognition of the drilling fluid as a vital factor in the success of many drilling operations. [2] Well drilling in Iraq is expensive due to the high cost of the imported chemicals used in the drilling fluid system to control the rheological properties. The aim of this study is to find out such local material which can be used safely as a thinner and as filtration rate reducer at the same time instead of the costly foreign material.

2-The Rheological Properties Of The Drilling Fluids
They are related to the flowing of the drilling fluid in the mud circulation system.
The rheological properties include the following:-2-1 Viscosity: It can be defined as a fluid resistance to flow. It is measured by Marsh funnel or rotational viscometer. The measuring unit is centipoises (C.P).
Viscosity depends on two components:       c.p,14 lb/100 ft 2 and 13 lb/100 ft 2 respectively but, when increasing temperature more than 150 F 0 ,the rheological values start to increase gradually and this is due to insufficient weight of additive which leads to solids flocculation inside drilling fluid.
At weights of 1,1.5,2 and 2.5 gm of the additive and with increasing both temperature and pressure ,the effectiveness of the local material is increased clearly due to the full additive solution inside drilling fluids especially at weight of 2.5 gm in which, at this rate and under the condition of 200 F 0 and 100 psi, the rheological properties are decreased significantly ,for example the apparent viscosity is 5 c.p (it was 17 c.p before addition),the plastic viscosity is 3 c.p (it was 7 c.p before addition),the yield point is 4 lb/100 ft 2 (it was 20 lb/100ft 2 ),and the gel strength is 5 lb/100ft 2 (it was 15.5 lb/100ft 2 ).
The weight of 2.5 gm for the additive can be considered as an ideal treatment for this type of drilling fluids.
At 3 gm of this additive, the rheological properties continued to fall in values up to 150 F 0 and 100 psi before they are increase again with increasing both temperature and pressure. This is due to solids conglomerate and the increase in solids content.
The results of the best model selection show that the power law and Casson models are the best for the two added thinners. Figures (14, 15, 16, and17) show the effect of local material on the rheological behavior for this type of mud.

6-Conclusions:
Depending on the results obtained in this study we can conclude the following:-

1-For fresh water mud:
There is a similarity in the behavior of the FCl and local material where the effect of the FCl was very effective especially at the weights (0.5-2.5) gm and has good thermal stability (till to 250 F 0 ) .The local was ideally efficient at weights (2-2.5)gm in terms of effectiveness and its tolerance to high temperatures The alkalinity of this mud with local material ranged (9.7-9.55) while with the foreign material was (8.5-9.44), thus the local material is better than the other material to some extent and that why this material is more stable and effective with increasing both temperature and pressure.

2-For salt mud:
There is somehow an obvious similarity in the behavior of the FCl and the local thinners to some extent, the local thinner works properly with increasing temperature and pressure at range (1-2.5) gm of the added thinner, while the FCl works properly at weights of 2 and 2.5 gm. In this type of mud the local thinner is better than the FCl to certain extent in relation to its low effect on alkalinity.