Studies on Some Egyptian Diatomite and Its Nano-Silica as Additive for Drilling Fluids and Oil Well Cementing

Abstract

This thesis targets to study samples of raw diatomite that exist in Egyptian environment in El-Fayoum Governorate at Qasr El-Sagha in northern shore of Birket Qarun. Diatomite represents remnants of freshwater life of old Lake Mories. It targets also to test diatomite and its nano-silica as additives in high filter loss squeeze slurry and oil well cementing after identifying different species in samples and making chemical analysis before and after nano-silica extraction. Diatoms are microscopic single-celled algae that are responsible for 25% of the O2 production and 40% of the organic carbon in the sea. 1.7 × 1012 kg annually input silica into the world’s oceans is cycled through diatoms. When diatoms die, their frustules sink to the bottom of the sea, which hardens into rock called diatomite. Diatomite has a variety of uses in different industries that take advantage of its chemical composition, porous structure, large surface area, and high liquid absorption capacity. 3D nano-silicon porous structures of diatom's frustule could make them ideal for nanotechnologists to use them in a broad range of nano-technological applications. Fortunately, micro-nano-materials make drilling fluid and oil well cementing with high-performance intelligent multiple functions and have greater potential. Drilling fluid, or mud, is the fluid that is circulated or pumped from the surface, down the drill string, through the bit, and back to the surface via the annulus. The main functions of the drilling mud are to provide hydrostatic pressure to prevent the reservoir fluids entering into the well bore, to carry out the drill cuttings, prevent caving, keep the drill bit cool and lubricate the tool, flood diesel oil or water to form an impermeable cake near the wellbore area and to suspend the cuttings while drilling is stopped. Drilling fluids could be classified into three major categories. Water Based Mud (WBM); Oil Based Mud (OBM) and Gas Based Mud (GBM). Selection of the best fluid to meet anticipated conditions will minimize well costs and reduce the risk of catastrophes such as stuck drill pipe, loss of circulation, gas kick, etc. Lost circulation is a common and expensive problem encountered during oil and geothermal drilling. Lost Circulation is the term used to describe the condition characterized by a lack of mud returning to the surface after being pumped down a well-bore. Drilling fluids may be lost into the natural fissures, high permeability formation or pressure induces fractures known as loss zones. Egyptian oil field production is distinguished by loss of circulation due to the rocky nature and the high porosity of Egyptian wells. Diatomite can be combined with other materials to be used as a lost circulation control material in drilling fluids. It allows filtrate to be lost from the slurry depositing a firm filter cake within the fracture itself which can be used to seal wide fractures. HFLS can be used against all types of lose zones. When loss zones consist of major fractures that are large and cannot be plugged by LCM the use of water based bentonite mud and additives are normally ceased. It can be sealed by withdrawing the drill string from the hole and injecting hard plug as cement which will enter the fractures then solidify to seal them. Diatomite is used as a natural pozzolan to produce lightweight slurries for cementing applications. In recent years great efforts have been done to improve drilling and oil well cementing properties to fixe the most common problems during drilling, using nano-particles. Addition of nano-material reduces the cost because the amount of nano-materials required for any utilization is much small. Results of this thesis are divided into three main chapters. First chapter contains the results of examination, identification, counting and microscopic photographing of fourteen collected