Unconsolidated

If we consider a well trajectory from surface to total depth (TD) it is sensible to look at the shallow section and the intermediate and reservoir intervals separately. The shallow section, usually referred to as top hole consists of rather unconsolidated sediments, hence the formation strength is low and drilling parameters and equipment have to be selected accordingly. 

The term porosity refers to the fraction of the medium that contains the voids. When a fluid is passed over the medium, the fraction of the medium (i.e., the pores) that contributes to the flow is referred to as the effective porosity of the media. In a general sense, porous media are classified as either unconsolidated and consolidated and/or as ordered and random. Examples of unconsolidated media are sand, glass beads, catalyst pellets, column packing materials, soil, gravel and packing such as charcoal. 

Permeability is defined as a measure of a rock s ability to transmit fluids. In addition to a rock s being porous, sedimentary rock can also be permeable. Permeability refers to the property of a rock that allows fluids to flow through its pore network at practical rates under reasonable pressure differentials. The quantitative definition of permeability was first given in an empirical relationship developed by the French hydrologist Henry D Arcy who studied the flow of water through unconsolidated sands [31]. 

Soil, from the engineering point of view, is defined as any unconsolidated material composed of discrete solid particles that has either liquids or gases in the voids between the individual particles. 

Select a tungsten carbide bit with shorter chisel inserts and less offset if the formations become more abrasive and unconsolidated. Use bit type 6-3 or 6-4. 

Rubber Sleeve Core Barrels. Rubber sleeve core barrels are special application tools designed to recover undisturbed core in soft, unconsolidated formations. As the core is cut, it is encased in the rubber sleeve that contains and supports it. Using face discharge ports in the bit, the contamination of the core by circulating fluid is reduced. The rubber sleeve core barrel has proven to be a very effective tool, in spite of the fact that the rubber sleeve becomes weak with a tendency to split as the temperature increases about 175°F. 

Equation 4-207 is used in carbonates (limestone and dolomite) and Equation 4-208 is used in unconsolidated to medium consolidated sandstones. A third Equation 4-209 can be used in highly consolidated sandstones. This is... 

The formation may be reactive and swell. It may be unconsolidated and collapse on the tool joints or drill collars. We may have mobile formations such as gumbo shales or salt beds in a plastic condition. 

Equation 4-258 gives better results in most formations, particularly in unconsolidated formations. Both of these equations show a variation of the transit time with the porosity. Since the porosity increases in overpressured zones, the transit time increases. Figure 4-333 shows a typical plot for the shale formations of a well in Jefferson County, Texas. 

Ruch, R.R. Kennedy, E.J. Shimp, N.E. Distribution of Arsenic in Unconsolidated Sediments from Southern Lake Michigan. Environ. Geol. 1979 Notes 37, 1-16. 

Manheim, F. T. (1970). The diffusion of ions in unconsolidated sediments. Earth Planet. Sci. Lett. 9, 307-309. 

The sediment reservoir (1) represents all phosphorus in particulate form on the Earth s crust that is (1) not in the upper 60 cm of the soil and (2) not mineable. This includes unconsolidated marine and fresh water sediments and all sedimentary, metamorphic and volcanic rocks. The reason for this choice of compartmentalization has already been discussed. In particulate form, P is not readily available for utilization by plants. The upper 60 cm of the soil system represents the portion of the particulate P that can be transported relatively quickly to other reservoirs or solubilized by biological uptake. The sediment reservoir, on the other hand, represents the particulate P that is transported primarily on geologic time scales. 

Simoneit, B.R.T., Philip, R.P., Jeden, P.D. and Galimov, E.M. (1984) Organic geochemistry of Deep Sea Drilling Project sediments from the Gulf of California - Hydrothermal effects on unconsolidated diatomic ooze. Org. Geochem., 17, 173-205. 

Horizontal completions in unconsolidated formations are being enhanced by a hydrochloric acid (HCl) breaker system for well clean up. Typically, the use of HCl in open-hole environments is avoided because of wellbore stability concerns. However, HCl successfully removes salt fluid loss control materials in wells without noticeable hole collapse [33]. 

P. D. Nguyen, J. D. Weaver, and J. L. Brumley. Stimulating fluid production from unconsolidated formations. Patent US 6257335, 2001. 

Unconsolidated or weakly consolidated sediments sometimes collapse around the well screen before the filter pack can be installed. This phenomenon is called formation collapse . Formation collapse can occur as a result of the inherently unstable nature of certain sediments or the disruptive nature of the drilling process. Formation collapse is most common below the water table. Although steps can be taken to minimize the amount of collapse, it may not be entirely preventable. The groundwater monitoring plan may need to accept natural formation material as the filter pack for some or all of the screen section. Well development activities (see Section 2.1.6) can be designed to maximize the effectiveness of the formation collapse materials as a filter pack. 

Density of soil in place by the sleeve method Unconsolidated undrained compressive strength of cohesive soils in triaxial compression... 

Grouted barriers use a variety of fluids injected into a rock or soil mass, which is set in place to reduce water flow and strengthen the formation. Grouted barriers are seldom used for containing groundwater flow in unconsolidated materials around hazardous waste sites because they cost more and have lower permeability than bentonite slurry walls. Nevertheless, they are suited to sealing voids in rock for waste sites remediation. 

Subsurface formations can be divided into the overburden (unconsolidated) and bedrock according to its solidarity. The upper subsurface can be further divided into the unsaturated zone and the saturated zone depending on pore structure and moisture saturation. The saturated zone is the zone in which the voids in the rock or soil are filled with water at a pressure greater than atmospheric. The water table is at the top of a saturated zone in an unconfined aquifer. The unsaturated zone is the zone between the land surface and the water table, and is also called the zone of aeration or the vadose zone. The pore spaces contain water at less than atmospheric pressure, air, and other gases. This zone is unsaturated except during periods of heavy infiltration. 

Gravel pack. Gravel pack and perforated completions are used where unconsolidated sands in the injection zone must be supported. In gravel-pack completions the cavity in the injection zone is filled with gravel or, more typically, a screen or liner is placed in the injection-zone cavity before the cavity is filled with gravel. In perforated completions, the casing and cement extend into the injection zone and are then perforated in the most permeable sections. In 1985, 53% of Class I wells were perforated and 17% were screened.20... 

The (compositionally) simplest mineral class comprises the native elements, that is, those elements, either metals or nonmetals that occur naturally in the native state, uncombined with others. Native gold, silver, and copper, for example, are metals that naturally occur in a ductile and malleable condition, while carbon - in the form of either graphite or diamond -and sulfur are examples of nonmetallic native elements. Next in compositional complexity are the binary minerals composed of two elements a metal or nonmetallic element combined with oxygen in the oxides, with a halogen - either fluorine, chlorine bromine, or iodine - in the halides, or sulfur, in the sulfides. The oxide minerals, for example, are solids that occur either in a somewhat hard, dense, and compact form in mineral ores and in rocks, or as relatively soft, unconsolidated sediments that melt at moderate to... 

Most of the rocks that make up the upper crust of the earth lie hidden beneath layers of sediments, unconsolidated accumulations of particles derived from the weathering of minerals and rocks (see Fig. 44 and Textbox 45) (Keller 1957). Once formed, the particles are either carried away or moved by the wind, rain, and gravitational forces into the seas and oceans or, before they get there, into depressions in the land. There they accumulate in a wide range of shapes and sizes (see Table 49) (Rocchi 1985 Shackley 1975). 

Soil is a relatively thin layer of unconsolidated matter on the surface of the earth, in which there is biological activity. The bulk of most soil consists of a mixture of extremely small, loose particles of minerals and organic matter the mineral particles are derived from the weathering of rocks the organic matter from the dead remains of living organisms (Rowell 1994 Limbrey 1975). The composition and texture of the soil are altered by human habitation humans change the natural flora and fauna of entire areas, their activ-... 

Table V. Mineral Fines Production From Unconsolidated Test Columns...

---