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Abstract The present techniques of air or gas drilling and their advantages and disadvantages are discussed. The relative merits of both air and mud drilling provide the basis for the advent of aerated fluids. For the purpose of this discussion, aerated fluids are divided into two phases:physical composition and circulation techniques. From the previous comparison, conclusions are drawn with respect to the future of aerated fluids. Introduction The advent of aerated fluids was a result of an attempt to avoid the limitations and yet maintain the advantages of both conventional drilling muds and air or gas when used as a drilling medium. A brief philosophical review of the petroleum industry and a summation of air and gas drilling characteristics provide the foundation for this discussion of the development and the characteristics of aerated drilling fluids. Many technological advancements into industry can often be attributed to either or both of two major demands:a physical demand for new processes in order to accomplish heretofore technically unfeasible tasks, or the economic demand for an improvement of present techniques that were formerly considered prohibitive from a sound investment viewpoint. The advent of aerated drilling fluids may be attributed to both demands. Since drilling and completion annually of over 45,000 oil and gas wells provides a total operational outlay exceeding 30 per cent of the entire producing companies' expenditures, a small technological, and eventually in economic advancement, can be of paramount importance. It appears that the most promising fields of improvement in drilling operations lie within three problems:the proper completion procedures for productive formations which have been damaged by the present drilling techniques, the reduction of lost circulation costs, and the reduction of the over-all operational drilling costs.
This paper was prepared for presentation at the 1998 SPE Annual Technical Conference Conference and Exhibition held in New Orleans, USA, 27-30 September 1998.
Abstract Most new methods of oil well drilling achieve increased rates of penetration essentially by increasing the mechanical power input to the rock over the maximum practical power level obtainable by conventional rotary drilling. However, whether this would decrease the drilling cost per foot of hole depends upon other factors as well, such as the cost of operation per unit time, well depth and the distribution of rocks of various drillabilities at the well site. Introduction Rotary drilling, introduced about 1900, is today the most widely used method of drilling oil wells in this country. The past 50 years have seen great strides in improved equipment and techniques for rotary drilling. However, the limitations of rotary drilling have long been recognized and there have been many attempts to develop new drilling methods to supplement or to supplant rotary drilling. The potentialities of some of these new drilling methods for decreasing the cost of drilling oil wells are discussed herein. Drilling Rate and Mechanical Power One significant result of a study of the fundamentals of rock drilling made at Battelle is that the fracture of brittle rock from the bottom of a hole by repetitive, indexed mechanical loading involves the expenditure of a certain amount of mechanical energy per unit volume of rock fractured out. Therefore, the rate of penetration of any mechanical drilling machine would be essentially directly proportional to the mechanical power developed in the rock per unit area of hole and inversely proportional to the drilling strength, which is the energy required to fracture off a unit volume of rock. Limitations of Rotary Drilling The mechanical power output to the rock for conventional rotary drilling is proportional to the torque required to turn the bit at the bottom of the hole and to the rate of rotation of the bit. The torque reaction to rotation associated with a given amount of static weight loading on the bit is less for the rocks of greater drilling strength. Since less mechanical power is developed in rocks of greater strength, the rate of penetration decreases more rapidly than in inverse proportion to the drilling strength. There is, consequently, a wide range in the drilling rates obtained by rotary drilling, perhaps about 50 to 1 from the weakest to the strongest rock of interest in oil well drilling.
Once again, we find ourselves in a time of extreme challenges on many fronts in the arena of well construction, with corresponding needs for technological advancements. Anyone who has been around the drilling-and-completion world during the past several years can attest to the unique environment in which we operate today. Ever-increasing drilling depths and formation temperatures and pressures are combined with depletion of mature basins and unprecedented geopolitical uncertainty. The good news is that human innovation and problem solving continue to accelerate commensurate with these challenges. In this feature, we specifically highlight the persistent need for high-performance drilling fluids.
- North America > United States > South Dakota > Williston Basin (0.99)
- North America > United States > North Dakota > Williston Basin > Three Forks Group Formation (0.99)
- North America > United States > Montana > Williston Basin (0.99)
- Well Drilling > Pressure Management (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (0.73)
- Well Drilling > Drilling Operations > Directional drilling (0.55)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (0.53)
Abstract The conventional drilling approach of employing a drillstring and bottomhole assembly with bit for drilling purposes and eventually running a casing string includes several tripping operations that leave the wellbore open for extended periods of time as an alternative to drilling-with-casing operations where the bottomhole assembly is attached to the casing. This eliminates additional drillstring tripping as drilling and running casing are performed simultaneously. This type of application reduces the number of string trips needed to complete a section, thus saving operational time and associated costs. As the diameter of a casing is larger than a drillstring, this method generally increases the Equivalent Circulating Density (ECD) as pressure losses increase owing to the reduction of the open hole and casing string annulus area. Casing directional drilling operations provide a much narrower drilling window with regards to restrictions in the annulus thus increasing the chances of reaching fracture pressure compared with conventional drillstring operations. To negate the resultant increase in ECD, the rheological profile of the drilling fluid must be designed appropriately. This paper discusses a unique oil-based drilling fluid system weighted with treated micronized barite slurry (TMBS) that has more recently been developed and used successfully in the Eldfisk field of the Greater Ekofisk area, Norway. The drilling fluid system provides low viscosity and a relatively low flat rheology, reduced torque values, and superior sag stability, thus delivering a fluid of low ECD contribution, low-pressure peaks, very effective hydraulics performance and static stability. These exceptional fluid characteristics make the system an excellent solution for drilling sections where the difference between pore pressure and fracture pressure is narrow. This was particularly so in this case where the stability of the fluid from sag potential was crucial for the improved success of the drilling-with-casing operation. Any solids sag onto the latching tools or bottomhole assembly (BHA) with the casing could have caused interference. The system had been used before for differing hole conditions including managed-pressure drilling and extended-reach wells, in high-temperature, high-pressure (HTHP) wells, and now with competence in a casing directional drilling operation. Introduction With this being the first offshore directional drilling work there is limited experience to draw from. To support the deviated drilling with casing operations comprehensive engineering studies were performed to qualify acceptable drilling parameters. This Eldfisk well on the 2/7B platform was the first offshore deviated drilling-with-casing operation ever performed (Fig. 1). The wellbore inclination was increased to a maximum of 69 degrees at the total depth of the second section while drilling with casing. The main purpose of drilling with casing operations is that drilling and casing running operations are conducted simultaneously. By operating in this manner the wellbore is secured at all times from less significant instabilities, and the drillstring tripping time and pipe handling time is dramatically reduced. This is because the BHA is being pulled on wireline for reconfiguration or bit change. The BHA latches into a purposefully designed sleeve in the casing shoe joint. When drilling with casing, the casing is rotated slowly, that is with a rotation per minute rate of less than 30. This rotation assists by "smearing" the drill cuttings into the formation of the wellbore. It helps provide an effective barrier that has been known to prevent the loss of drilling fluid into the formation. This can be quite contrary to conventional drilling operations with a drillstring where the drillstring can aggressively bounce at the wall resulting in the removal of the filter cake in permeable formations. As a consequence the formation could be exposed to the drilling fluid and its higher hydrostatic pressure causing fracturing or a reduction in the formation integrity.
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/7 > Greater Ekofisk Field > Eldfisk Field > Tor Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/7 > Greater Ekofisk Field > Eldfisk Field > Hod Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > PL 018 > Block 2/7 > Greater Ekofisk Field > Eldfisk Field > Ekofisk Formation (0.99)