|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
The causes of mechanical pipe sticking are inadequate removal of drilled cuttings from the annulus; borehole instabilities, such as hole caving, sloughing, or collapse; plastic shale or salt sections squeezing (creeping); and key seating. Excessive drilled-cuttings accumulation in the annular space caused by improper cleaning of the hole can cause mechanical pipe sticking, particularly in directional-well drilling. The settling of a large amount of suspended cuttings to the bottom when the pump is shut down, or the downward sliding of a stationary-formed cuttings bed on the low side of a directional well can pack a bottomhole assembly (BHA), which causes pipe sticking. In directional-well drilling, a stationary cuttings bed may form on the low side of the borehole (see Figure 1). If this condition exists while tripping out, it is very likely that pipe sticking will occur.
The rubble zone that might lie beneath or adjacent to the salt section usually consists of a series of highly reactive shale stringers that are embedded in unconsolidated sand. The zone could be overpressured at the entry point because of a gas pocket under the salt, then underpressured for the remainder of the section. Catastrophic mud loss below the salt is the most challenging of these problems and prevents most operators from drilling rubble zones with oil-based fluids (OBFs) and synthetic-based fluids (SBFs). The decision about whether to use an SBF or a salt-saturated water-based fluid (WBF) usually is based on the known risk of lost returns. The SBF can provide increased drilling efficiency and a faster rate of penetration (ROP), but a salt-saturated WBF provides adequate control over hole enlargement and might be preferable where the potential for large losses exists.
Hole cleaning is the ability of a drilling fluid to transport and suspend drilled cuttings. Throughout the last decade, many studies have been conducted to gain understanding on hole cleaning in directional-well drilling. Laboratory work has demonstrated that drilling at an inclination angle greater than approximately 30 from vertical poses problems in cuttings removal that are not encountered in vertical wells. Figure 1 illustrates that the formation of a moving or stationary cuttings bed becomes an apparent problem, if the flow rate for a given mud rheology is below a certain critical value. The most prevalent problem is excessive torque and drag, which often leads to the inability of reaching the target in high-angle/extended-reach drilling.
There are two fundamental problems that make accurately estimating the productivity of a horizontal well more difficult than estimating the productivity of a vertical well. The theoretical models available have a number of simplifying assumptions and the data required for even these simplified models are not likely to be available. Still, we must make estimates and decisions based on those estimates. In this page, two productivity models that have proved useful in practice are discussed. The first, published by Babu and Odeh in 1989, is limited to single-horizontal wells.
Openhole completions provide another opportunity for sand control. Many engineers do not routinely think of performing an openhole completion when confronted with selecting a completion. This is true probably because cased-hole completions are so widely accepted and because they are not familiar with selection criteria and procedures. Openhole completions can provide excellent, high-productivity completions, but they must be applied under the right reservoir conditions. They avoid the difficulties and concerns of perforation packing and reduce the gravel-placement operations to the relatively simple task of packing the screen/openhole annulus.
Electromagnetic heating has a different effect on heavy oil reservoirs than other enhanced oil recovery processes that use heat. This article describes the ways in which electromagnetic heating can be applied to a reservoir. As shown in Figure 1, Q(t), the time-dependent rate of production of a given reservoir with either horizontal or vertical wells, depends on the flow of oil through the reservoir and through the producing wells. In the reservoir, the flow is conditioned by a temperature-dependent viscosity, μ(T), porosity, permeability, and compressibility (Φ, k, and c). To a first approximation, the last three parameters are unchanged by the heating.
The Department of the Interior issued the final environmental study for its plan to open up drilling in the Arctic National Wildlife Refuge, reportedly putting the government on track to sell oil and gas leases there later this year. Snow depths on Alaska’s North Slope have thinned this year, the University of Alaska Fairbanks said in a study, creating a possible obstacle for exploration in part of the Arctic National Wildlife Refuge thought to harbor more than 7 billion bbl of oil. A bipartisan group of House lawmakers introduced legislation that would ban oil and natural gas drilling in Alaska’s Arctic National Wildlife Refuge.
The Department of the Interior issued the final environmental study for its plan to open up drilling in the Arctic National Wildlife Refuge, reportedly putting the government on track to sell oil and gas leases there later this year. A bipartisan group of House lawmakers introduced legislation that would ban oil and natural gas drilling in Alaska’s Arctic National Wildlife Refuge.
Environmentalists have sued a US agency to try to stop it from allowing oil and gas drilling on a vast stretch of federal land in Nevada, where the government is reversing protections put in place 9 months ago under the Obama administration. The US Interior Department on 7 August launched an overhaul to an Obama-era plan to protect sage grouse that it says aims to preserve the species of bird while expanding opportunities for oil development in western states where they live. The federal government is barred from auctioning off new drilling rights on public lands in California for at least another year under a settlement reached with environmental groups, one of the groups told Bloomberg.