Aqueous-based oil well drilling fluids containing high amylose starch polymers

#The invention relates to aqueous fluids used for drilling of oil, gas and geothermal wells in earth formations, and to additives for use in such fluids. More particularly, the invention relates to an aqueous-based drilling fluid containing specific types of starch. The starches are used to improve various qualities of such fluids, most specifically to control filtrate losses, while having a minimum impact on viscosity.

#Most specifically, this invention relates to high amylose content starches used in well drilling fluids and to well drilling fluids produced therefrom. It has been surprisingly discovered that such starches provide filtrate loss control properties to drill fluids equal to or better than traditional starches but do not present the unwanted Theological increases to the fluids that such traditional starches cause.

#Many inventions relate to drilling fluids and their additives. Drilling fluids technology is the application of scientific knowledge, engineering principles and the knowledge of chemistry to a specific industrial development. Drilling fluids technology therefore involves the sciences of geology, chemistry, and physics, and the skill of engineering. Its goal is the utilization of materials both old and new to attain at low cost, if possible, the desired objective of each excavation to lead to the discovery of oil or gas for both the benefit of private enterprise and the national good.

#Starches as indicated below were provided and formulated into model drilling fluids which were tested for fluid loss and rheological properties.

#All fluids were prepared and tested according to standard API mud preparation guidelines using standard malt cups and a 5 spindle Hamilton Beach multimixer. The prepared fluids were placed in 316 stainless steel heat age cells. The cells were placed in a roller oven set at the desired temperature and hot rolled for the desired time. The cells were taken out and quenched in a sink filled with cold water. API test methods were then conducted, recording the mls of fluid lost. The fluids were then replaced in the heat age cells and hot rolled for another cycle . The process was continued until degradation of the starch occurred. Rheological measurements were taken initially and after each hot roll cycle using a Fann model 35 Rheometer. Measurements were taken as per API RP 13B proceedures.

#Base Mud Formulation