Common Failures In Onshore Oil & Gas Wells

Common Failures In Onshore Oil & Gas Wells

In the pursuit to further understand the challenges faced by oil and gas operators, Viking has maintained a failure database capable of determining common failures and failure trends. This information provides insight to aid in preventing common failures and improving industry practices to reduce incident rates in addition to saving time and money.

Failures Related to API 5CT High Strength Steels

American Petroleum Institute (API) 5CT high strength steels are extensively used for casing strings inwells subjected to high cyclic hydraulic fracturing loads. While non-sour grades of API steel such as P110 casing strings have been used satisfactorily for well construction, standard API P110 connections have seen higher rates of failures than pipe body failures in shale wells that require hydraulic fracturing.

Practical Guidelines for the Diagnosis and Remediation of Pipeline Blockages

One of the primary flow assurance challenges in the production of hydrocarbons is the prevention of pipeline blockages. Blockages can occur from a combination of improper system design, improper selection of piping and insulation materials, production chemistry aspects, inadequate or improper commissioning, startup and operating procedures, deviation from the proven operating procedures, changes in the operating conditions, intervention operations and improper maintenance procedures. The nature of the blockages can vary from "not-so-severe" to "hard-to-remediate" depending on the type of blockage.

Collapse Strength of Casing Subjected to Combined Load

Collapse Strength of Casing Subjected to Combined Load

Triaxial evaluation of wellbore loads is used extensively for casing and tubing string design and analysis. A triaxial based collapse strength method was recently adopted by the American Petroleum Institute (API), and an addendum issued to API Technical Report 5C3 (TR 5C3). The triaxial based collapse formula incorporates internal pressure and axial load into the calculation of casing and tubing collapse strengths.  Casing and tubing that are subjected to combined loads have higher collapse strength than previous formulas would predict, permitting the use of thinner walled, or lower strength, pipe than formerly required. 

Collapse Strength of Casing Subjected to Combined Load

Triaxial evaluation of loads is used extensively for casing and tubing string design and analysis. The paper presents a method of determining the triaxially based collapse strength of casing and tubing subjected to simultaneous axial and internal pressure loads. The triaxially based collapse strength method was recently adopted by the American Petroleum Institute (API) and an addendum issued to API Technical Report 5C3 (TR 5C3). Casing and tubing subjected to combined loads have higher collapse strength than previous formulas predict.

Advanced Technology Solutions for Next Generation HPHT Wells

This paper describes research efforts and technology development associated with the next generation of high pressure, high temperature (HPHT) well designs. Sometimes referred to as x-HPHT (extreme HPHT), work has been ongoing for several years looking at the next generation of HPHT wells for both subsea and shelf/onshore operations. A large number of challenges arise when addressing the engineering of HPHT wells.

Joining of Dissimilar Aluminum Alloys and Other Metals and Alloys by Friction-Stir Welding,

A wide range of aluminum alloys and other metals and alloys, particularly dissimilar materials, have been friction-stir welded in this study. These include Al 5052/Al 7075, Al 7075/Al 2017, Al 5052/Al 2017, Al 7×1×(Sc)/Al 7×5×(Sc), Cu/brass, and 6061 Al with a thin Cu sheet in the butted seam to observe particulate flow in the dynamically recrystallized regime which facilitates solid-state welding.

Flow Patterns During Friction Stir Welding

Friction Stir Welding is a relatively new technique for welding that uses cylindrical pin or nib inserted along the weld seam. The nib (usually threaded) and the shoulder in which it is mounted are rapidly rotated and advanced along the seam. Extreme deformation takes place leaving a fine equiaxed structure in the weld region. The flow of metal during Friction Stir Welding is investigated using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes.

Metal Flow During Friction Stir Welding

The flow of metal during Friction Stir Welding is clarified using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes. The first is a wiping of material from the advancing front side of the nib onto a plug of material that rotates and advances with the nib. The material undergoes a helical motion within the plug that both rotates and advances with the plug and descends in the wash of the threads on the nib and rises on the outer part of the plug.

Improved Integral Joint Casing Connections Can Reduce Well Costs

Improvements in integral joint connections (IJC) for casing in the past decade have allowed operators to drill wells previously not feasible to drill for economic or technology reasons.
New integral joint connections can withstand greater loads, increasing their range of applications. The use of IJC casing can allow a slimmer well to be drilled, reducing total well costs.

Designer Casing for Deepwater HPHT Wells

 Deepwater high pressure, high temperature (HPHT) drilling environments present difficult challenges to well engineers. Typical deepwater pore pressure and fracture gradient profiles result in a narrow drilling window that can lead to seven to nine casing points. The high cost of these wells demands a high rate completion for economic payback, which defines the size of the production casing and liners. Drilling casings are restricted by the standardized 18-3/4" through bore diameter dictated by high pressure wellhead housings, blowout preventers, and riser systems. Furthermore, high pressures require thick wall casing, especially if sour service materials are specified. Satisfying all of these pressure and geometrical constraints requires some unconventional practices.

LRFD Derived Performance of a Qualified API Connection Population

Tubular products are among the most critical items in a well, and the threaded connection can represent one of the more complicated and limiting mechanical features for tubular products. Previous tubular design methodology did not specifically address threaded connections, rather it applied safety factors to pipe body ratings. In contrast, Load and Resistance Factor Design (LRFD) methods specij7cally address connection performance. This work is a discussion of how the limit performance is being defined and quality systems are being revised for API connections in accordance with the objectives of the LRFD method for OCTG.

Tubing Temperature Correlations For Injection and Production Based on Simulation and Field Experience

A finite difference model was developed and used to simulate transient heat transfer in wells undergoing injection and production processes. The tubing temperature profiles from these simulations were then reduced to a set of algebraic equations to provide simple and effective temperature versus depth and temperature versus time estimates. Results from field tests are also presented and compared in order to validate the finite difference model.

Optimization of HPHT Wells: Reducing the Cost of Design Integrity

Optimization of easing and tubing designs for critical wells has become increasingly important for economic reasons. This paper describes an investigation into the relationship between design criteria (minimum acceptable design factors and maximum acceptable number of pipes) and cost. The measurement of design integrity by both design factors and by probability of failure was evaluated with respect to reduction of costs. The results indicate that significant cost reductions, often on the order of 10-20%, are available by optimization of the string design.