Information_wellprep

Well Preparation

DHVI is committed to ensuring every job we do is a successful video survey. The sales and operations staff of the company makes every attempt to work with our customers in planning the job to discuss well prep procedures and operational plans.

The prerequisite for successful downhole video is a clear transparent fluid in the wellbore in the area of interest (ex., clear water, dry gas, or air). Successful downhole video begins with proper planning and consideration of potential sources of opaque fluids and associated countermeasures to ensure a clear viewing medium. Opaque fluids prohibit viewing the object(s) of interest. The majority of opaque wellbore is caused by silt or sand entry in a continuous phase of water or by gas production in a water phase. Most opaque fluid sources can be cleaned up with proper planning and clean, clear, water, or nitrogen or gas displacement.

Often, little or no well preparation is needed for a successful video log. In these cases, the area of interest for viewing is either in air, gas, or clear water.

Crude oil, although opaque, no longer sounds the "death rattle" to video logging it once did. A highly specialized lens preparation surfactant, developed in the early 1990s, overcame the affinity of crude oil to wet and adhere to glass. The surfactant repels oil, preventing it from adhering to the camera optic port that is in front of the video camera lens. The surfactant broadened the applications and success of downhole video so that oil in a well is rarely a problem when video logging. Through the successful use of downhole video, it was learned that oil and water tend to quickly separate into their respective phase upon entry into the well. This usually provides a very good viewing area throughout the producing interval. If a continuous phase of oil is encountered, the oil will obscure the view until the camera encounters another continuous phase of clear fluid. The lens surfactant was a milestone in video logging, allowing operators to survey idle wells containing a thick pad of oil without the need of a rig. In most wells with either a competent formation or a well completion designed to act as a competent formation, the produced water is clear and the camera can see in the water. Because the produced water is flowing through the tortuous path of the formation, the formation acts as a filter to bridge off fines and bring in the now clean, clear, water. The condition of the water on most wells can be inspected before video logging by taking a sample of the produced fluid at the wellhead and letting it set for a time. Samples from oil producers are emulsified at the surface but the oil and water eventually separate, leaving a pad of oil on top of a column of clear water usually within 24 hours. If the water sample is still not clear after 24 hours, thought needs to be given to why it is not and what can be done to achieve a clear medium downhole at the object of interest. When the wellbore fluid is air or gas, well preparation may still be needed to clean up the well though they are usually simpler than water/oil producers. When the objective of the video log is a fluid entry survey, collect a sample of produced fluid at the wellhead to check the clarity of the produced water before job call out to ensure a successful video log can be achieved. Allow the sample to settle for 12 to 24 hours. The oil and water will stratify and if the produced water is clear, conditions are good for the video log. The water column at the bottom of producing wells is usually clear, providing optimum viewing conditions without special well preparation. For further information on well preparation for downhole video logging, consult technical paper SPE 35680. This paper contains the "what to" and "how to" for video logging problem wells.

Copyright © 1997-2003 DHV International Inc. All rights reserved.

Well Preparation
	DHVI is committed to ensuring every job we do is a successful video survey. The sales and operations staff of the company makes every attempt to work with our customers in planning the job to discuss well prep procedures and operational plans.
The prerequisite for successful downhole video is a clear transparent fluid in the wellbore in the area of interest (ex., clear water, dry gas, or air). Successful downhole video begins with proper planning and consideration of potential sources of opaque fluids and associated countermeasures to ensure a clear viewing medium. Opaque fluids prohibit viewing the object(s) of interest. The majority of opaque wellbore is caused by silt or sand entry in a continuous phase of water or by gas production in a water phase. Most opaque fluid sources can be cleaned up with proper planning and clean, clear, water, or nitrogen or gas displacement. Often, little or no well preparation is needed for a successful video log. In these cases, the area of interest for viewing is either in air, gas, or clear water. Crude oil, although opaque, no longer sounds the "death rattle" to video logging it once did. A highly specialized lens preparation surfactant, developed in the early 1990s, overcame the affinity of crude oil to wet and adhere to glass. The surfactant repels oil, preventing it from adhering to the camera optic port that is in front of the video camera lens. The surfactant broadened the applications and success of downhole video so that oil in a well is rarely a problem when video logging. Through the successful use of downhole video, it was learned that oil and water tend to quickly separate into their respective phase upon entry into the well. This usually provides a very good viewing area throughout the producing interval. If a continuous phase of oil is encountered, the oil will obscure the view until the camera encounters another continuous phase of clear fluid. The lens surfactant was a milestone in video logging, allowing operators to survey idle wells containing a thick pad of oil without the need of a rig. In most wells with either a competent formation or a well completion designed to act as a competent formation, the produced water is clear and the camera can see in the water. Because the produced water is flowing through the tortuous path of the formation, the formation acts as a filter to bridge off fines and bring in the now clean, clear, water. The condition of the water on most wells can be inspected before video logging by taking a sample of the produced fluid at the wellhead and letting it set for a time. Samples from oil producers are emulsified at the surface but the oil and water eventually separate, leaving a pad of oil on top of a column of clear water usually within 24 hours. If the water sample is still not clear after 24 hours, thought needs to be given to why it is not and what can be done to achieve a clear medium downhole at the object of interest. When the wellbore fluid is air or gas, well preparation may still be needed to clean up the well though they are usually simpler than water/oil producers. When the objective of the video log is a fluid entry survey, collect a sample of produced fluid at the wellhead to check the clarity of the produced water before job call out to ensure a successful video log can be achieved. Allow the sample to settle for 12 to 24 hours. The oil and water will stratify and if the produced water is clear, conditions are good for the video log. The water column at the bottom of producing wells is usually clear, providing optimum viewing conditions without special well preparation. For further information on well preparation for downhole video logging, consult technical paper SPE 35680. This paper contains the "what to" and "how to" for video logging problem wells.

Copyright © 1997-2003 DHV International Inc. All rights reserved.