Because of the inherent curvature (angle build sections) and angled bottomhole segment of directional and horizontal wells, optimization of a progressive cavity pump (PCP) system design for such applications begins with the drilling program. The proposed well geometry, or directional plan, should take into consideration the design and operation attributes of a PCP system, including equipment selection, to contend with potential rod/tubing-wear and rod-string fatigue problems, the preferred pump seating location for achieving optimal production rates throughout the well life, and possible issues related to gas and solids production. The first line of defense against rod/tubing-wear and sucker-rod fatigue problems in deviated and horizontal wells is a good wellbore profile (see previous sections on rod-string/tubing wear and rod loading).
Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. For a strict definition, a 90o deviated well. Actually the well covers a range of "highly" deviated wells (80o to 90o). In the strictest terms, the deviation is measured as 90o from vertical, but tilting bedding planes may make the deviation to the bedding planes a different judgment.
While most types of logs are used to characterize the wellbore, formation, and fluids prior to well completion, a number of logging tools are available to provide information during production operations and beyond. This article discusses the various types of production logs and how they can often be used together to provide crucial information for understanding and resolving problems.. Production Logging is one of a number of cased hole services that includes cement monitoring, corrosion monitoring, monitoring of formation fluid contacts (and saturations), perforating and plug and packer setting. Services performed in dead, overbalanced, conditions can use relatively simple surface pressure control equipment and are often performed using large open hole style logging cables. Wells with surface pressure typically have a completion tubing of relatively small internal diameter, ID, compared to the casing size across the reservoir. This reduced ID means that cased hole toolstrings for live wells are typically sized at 1-11/16" in order to pass through the smallest nipple in a 2-3/8" tubing.
Horizontal wells are being employed in innovative ways in steam injection operations to permit commercial exploitation of reservoirs that are considered unfavorable for steam, such as very viscous oils and bitumen and heavy oil formations with bottomwater. For example, Chang, Farouq Ali, and George used scaled models to study five-spot steamfloods, finding that for their experimental conditions, a horizontal steam injector and a horizontal producer yielded the highest recovery. Huang and Hight carried out numerical simulations of a variety of hypothetical situations involving horizontal and vertical wells. A few field-tested applications of horizontal wells are briefly described next. Figure 1 – Comparison of the various injection-production strategies on ultimate oil recovery, for the different bottomwater cases investigated (after Chang, George, and Farouq Ali).
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.
As discussed in Source function solutions of the diffusion equation, the conventional development of the source function solutions uses the instantaneous point-source solution as the building block with the appropriate integration (superposition) in space and time. In 1973, Gringarten and Ramey introduced the use of the source and Green's function method to the petroleum engineering literature with a more efficient method of developing the source solutions. Specifically, they suggested the use of infinite-plane sources as the building block with Newman's product method.
As installed, casing usually hangs straight down in vertical wells or lays on the low side of the hole in deviated wells. Thermal or pressure loads might produce compressive loads, and if these loads are sufficiently high, the initial configuration will become unstable. However, because the tubing is confined within open hole or casing, the tubing can deform into another stable configuration, usually a helical or coil shape in a vertical wellbore or a lateral S-shaped configuration in a deviated hole. These new equilibrium configurations are what we mean when we talk about buckling in casing design. In contrast, conventional mechanical engineering design considers buckling in terms of stability (i.e., the prediction of the critical load at which the original configuration becomes unstable).
Horizontal wells are high-angle wells (with an inclination of generally greater than 85) drilled to enhance reservoir performance by placing a long wellbore section within the reservoir. Horizontal Well contrasts with an extended-reach well, which is a high-angle directional well drilled to intersect a target point.
This page discusses the primary manner in which the immiscible gas/oil displacement process has been used in qualitative terms. This is the use of gas injection high on structure to displace oil downdip toward the production wells that are completed low in the oil column. In many cases, an original gas cap was present, so the gas was injected into that gas cap interval (see Figure 1 for cross-sectional view of anticlinal reservoir with gas cap over oil column with dip angle α and thickness h). In this situation, the force of gravity is at work, trying to stabilize the downward gas/oil displacement process by keeping the gas on top of the oil and counteracting the unstable gas/oil viscous displacement process. If the oil production rate is kept below the critical rate, then the gas/oil contact (GOC) will move downward at a uniform rate.