How Statoil determined tubing and annular integrity

Overview 

Wells in mature fields often contain corrosion and scale that can mislead the sonic and ultrasonic tools used to verify cement and casing integrity. Statoil requested Halliburton to deploy its Multifinger Caliper (MFC) tool with its CAST-M™ (Circumferential Acoustic Scanning Tool) technology and a cement bond log (CBL) in an old North Sea well. Their goals: overcome conditions that could skew results, so that Statoil could take appropriate action and satisfy government environmental regulations. The combination of these three tools enabled engineers to positively verify liner and cement integrity before partially abandoning the well. The multitool solution reduced intervention time and abandonment costs by ensuring accurate data acquisition without multiple runs in the hole. In addition, the use of mono-conductor wireline allows for rigless logging and conveyance flexibility, which can further contribute to operational savings and technical solutions.

Challenge 

Verifying cement and casing integrity Statoil wanted to abandon part of a well where scale and corrosion would affect normal ultrasonic tool operation.

Identifying causes of bad readings Analysts could not tell whether corrosion or scale was skewing ultrasonic tool responses.

Inefficient data acquisition Statoil once was forced to relog many wells because of ambiguous results from first-run ultrasonic logs.

Solution

Combination of three tools Together, CAST-M, CBL-M and Multifinger Caliper tools created an unambiguous picture of well conditions.

Caliper tool reveals scale buildup Halliburton’s Multifinger Caliper tool detected solids buildup inside pipe that was undetected by acoustic tools.

New tool combination Statoil acquired all necessary data in one efficient run with good data quality and depth correlation.

Result  

Accurate readings Clearly seeing the difference between scale and corrosion satisfied regulators. P&A commenced.

Identified locations for plugs Knowing where casing/cement integrity remained intact enabled Halliburton to locate the best areas for setting plugs.

Quick, informed decisions Statoil made informed decisions that satisfied regulators and reduced risk in one quick, efficient run.