Gas Drilling Operations Research Articles

A study of wellbore stability in shales including poroelastic, chemical, and thermal effects

This paper presents the development of a model for determining wellbore stability for oil and gas drilling operations. The effects of mechanical forces and poroelasticity on shale behavior are included, as well as chemical and thermal effects. Chemical effects are caused by the imbalance between the water activity in the drilling mud and the shale water activity. The magnitude of this contribution depends on the effectiveness of the mud/shale system to perform as a semipermeable membrane. Experimental results show that osmotic pressures develop inside shales when they are exposed to different drilling fluids. This osmotic pressure is treated as an equivalent hydraulic potential, and is then added to the hydraulic wellbore and pore pressure as time progresses. Thermal diffusion inside the drilled formation induces additional pore pressure and rock stress changes and consequently affects shale stability. Thermal effects are important because thermal diffusion into shale formations occurs more quickly than hydraulic diffusion and thereby dominates pore pressure changes during early time. Rock temperature and pore pressure are coupled for most porous media studies; however, we have found that they can be partially decoupled for shale formations by assuming that convective heat transfer is negligible. The partially decoupled temperature and pore pressure effects can therefore be solved analytically under appropriate initial and boundary conditions. Experimental data for shale strength alteration, which occurs when shales are exposed to different fluids, are also included for the determination of cohesion strength decay. Pore pressure, collapse stress, and critical mud weights are variables investigated for determining poroelastic, chemical, and thermal effects on shale stability. The most important factors, which affect wellbore stability, are clearly identified.

Investigation of Factors Affecting Wear Characteristics in Rubber–Metal Sliding Contact

This paper examines the correlation between volumetric wear loss and the energy expended at the interface of nitrile rubber sliding on steel in the presence of drilling mud and abrasive sand. The measurement of energy expended at the material interface is investigated as an alternative for monitoring the extent of wear damage due to operating conditions. This is contrasted with running hours, as is typical of reciprocating mud pumps used in oil and gas drilling operations. It is found that increased deterioration and wear loss resulted from the combined effects of load and sand. The volumetric wear loss was found to increase at the rate of 16.8 per cent per 1 per cent sand and is specific to the type of sand used and the test configuration employed.

Polymer Technology for Waste Reduction and Stabilization (Oil and Gas Drilling Operations): ABSTRACT

The purpose of this paper is to address environmental issues associated with waste generated through drilling operations, the use of polymers to reduce wastes in a closed-system environment without the use of solids control, and methods of stabilization of drilling discharges using polymer technology. The objective is to demonstrate that with the proper use of polymers, waste can be reduced and stabilized in a cost-effective method, thereby reducing the volume that is generated and stabilization without a volumetric increase. The environment will be enhanced while reducing risks and costs. It is further outlined that the use of polymer technology will add little, if any, cost to the drilling operation.

Oil and Gas Drilling Operations in Kenya – A Selected Bibliography 1964–1988

Oil and Gas Drilling Operations in Kenya – A Selected Bibliography 1964–1988

Computer program for air or gas drilling

A user friendly microcomputer program has been developed for field engineers to design air or gas drilling schedules. This program will help drilling engineers predict the air or gas minimum volumetric requirements with good accuracy. In this program, Ikoku's air and gas drilling model was modified to make it much simpler to use in the field. Computer output data, such as air or gas flow rates and standpipe pressures, are critical to the efficient operation of air or gas drilling. This program has been tested against Ikoku's field operation manual and was in good agreement for all cases. Air or gas drilling has several advantages over conventional mud drilling operations where formation conditions are conducive to air or gas drilling methods. A key factor required in the design of air or gas drilling operations is the volume of air or gas needed to carry the bit cuttings to the surface. If the volume of air or gas is too low, cutting will slug in the hole due to insufficient lift force, and the penetration rate will be decreased. If the volume of air or gas is too high, drilling costs may increase and wellbore deterioration may result.

Global Look at High Pressures: ABSTRACT

Formation pressures higher than hydrostatic have been found in all parts of thw world during oil and gas drilling operations. The present paper analyzes the worldwide distribution of these high pressures. Data used include wells from western Europe, Hungary, Poland, Rumania, Russia, the Middle East, the Indian subcontinent, Australia, New Guinea, New Zealand, Japan, the Arctic, the African West Coast, the Red Sea, South America, and the United States. A statistical analysis to define the main geologic characteristics of high-pressure reservoirs was carried out using data from wells penetrating more than 5,000 reservoirs in the Gulf of Mexico, Santa Barbara Channel, and the Anadarko, Permian, and Uinta basins. The probability of finding high pressures in a given depth rang for each of these basins has been established. The main mechanisms responsible for the creation of these high pressures are concluded to be (1) gravitational compaction, (2) the montmorillonite-illite transformation, (3) wax seals, and (4) tectonic compression. Although in certain instances one of the mechanisms predominates, in most places a combination of them is responsible for the high pressures. Modeling of the geologic processes that have created a basin allows us to recognize in advance the type of pressures to be found there. End_of_Article - Last_Page 775------------