Method and apparatus for production logging

Abstract

Method and apparatus are disclosed for performing production logging in a cased well having a plurality of isolated production zones and a tubing string which intersects the production zones. An access device is connected in the tubing string for each of one or more production zones and an intervention tool is conveyed to and positioned in the access device associated with the selected production zone. Production parameters from the selected zone are measured by sensors in the intervention tool.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to method and apparatus for production logging in a cased, multilayer wellbore. [0003] 2. Description of the Prior Art [0004] Well logging surveys are often made in producing oil and gas wells to determine the volumetric concentration of the oil, gas and unwanted water components in the production flow. These data along with measurements of the fluid flow velocity, pressure and temperature may be used to determine production rates and other information from each zone of interest in the well. Such data are essential for the improvement of oil and gas production, reducing water production, managing the field reservoir, and optimizing production from the well. [0005] Obtaining reliable production information in deviated, multilayered, multi-phased reservoirs has proven to be a difficult task. This is due to segregation of the lower density phases, e.g. oil and gas, migrating to the high si...

AI Technical Summary

Benefits of technology

[0011] A method in accordance with the present invention comprises repeating the aforesaid steps for at least one more production zone in the well, and using the data respecting the measured parameters from the measured production zones to make decisions concerning the production from the well.

[0012] In accordance with the present invention apparatus is provided for use in production logging operations in a cased well having a plurality of production zones that are isolated from one another and a tubing string for conveying the production from the production zones to the earth's surface. Apparatus in accordance with the present invention comprises a plurality of access devices, which may be sliding sleeve devices and which are connected in the tubing string. At least one access device is connected in the tubing string for each of one or more production zones in the cased well. Apparatus in accordance with the present invention further comprises an intervention tool which is conveyed through the tubing string from the surface of the earth to a selected one of the access devices and is positioned in the access device that is associated with the selected production zone. One function that the intervention tool provides is to isolate the selected production zone from the other production zones. Once the intervention tool is positioned, the production flow from the isolated/selected production zone passes through the intervention tool, and the intervention tool contains sensors to measure parameters associated with the production zone corresponding to the access device in which the tubular member is positioned. The sensors may be selected from a group including those which measure pressure, density, temperature, capacitance/dielectric and velocity.

[0013] In accordance with the present invention, a production logging system is provided for use in a cased well having a plu

Problems solved by technology

Obtaining reliable production information in deviated, multilayered, multi-phased reservoirs has proven to be a difficult task.

This is due to segregation of the lower density phases, e.g. oil and gas, migrating to the high side of the hole where they cannot be adequately measured by centralized sensors.

Such sensors may have a very limited circumferential area of measurement and may not read globally.

Additionally, the heavier fluids, e.g. water, suffer from a phenomena known as “water fallback” where the heavier fluids falls back downhole, which may cause the velocity measurement to read an incorrect flow rate.

Fluid segregation and fallback thus prevent all current technology from providing reliable production data in the majority of deviated wellbores.

Another shortcoming of current production logging technology is that it can only measure pressure in the borehole or production tubing and not the actual reservoir pressure of an individual layer in a multilayer reservoir.

For example, production from hydrocarbon rich zones at relatively lower pressures may be delayed for the pressure to drop with the passage of time from production from higher pressure production zones.

A failure to properly balance this may cause hydrocarbons brought out of one production zone to flow back into another zone at lower pressure, causing lost production and perhaps damage to the latter formation.

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