New downhole coiled tubing (CT) technology was used to facilitate the success of a challenging fishing intervention and to verify the reliability and accuracy of CT operations/simulation software. The technology supplies the newly designed bottomhole assembly (BHA) with continuous power from, and fiber-optic communications with, surface equipment, enabling accurate, real-time monitoring of measurements of bottomhole conditions.
Uncertainty exists in operations using CT regarding whether the planned axial force is transmitted from the surface through the pipe to the BHA and whether the BHA is functioning according to plan. During fishing operations, unless the BHA applies a minimum amount of force (compression and/or tension) to the fishing neck, the particular intervention run will be unsuccessful. The BHA then needs to be returned to the surface without recovering the fish.
This paper presents a case study of a well located in the foothills of Colombia in which a perforating gun became stuck following an operational issue. This situation resulted in an oil production reduction of 30%. Several fishing attempts were performed using conventional CT to recover the stuck perforating gun and to restore production to its previous level.
The initial lack of real-time BHA data and the inherent nature of CT elongation and buckling led the operator to believe that the fish was being recovered to the surface; several runs were performed with unsuccessful results. A CT string, equipped with fiber-optic communications and a continuous power supply to the BHA, confirmed that the perceived movement of the fish was not real and that the BHA selected was not generating nor transferring the expected force to the fish. The force transmitted by the pipe and the upward/downward impact force generated by the jar were measured in real time and determined to be consistent with simulated forces; the BHA configuration used for the operation was then redesigned. The new design led to the successful recovery of the fish and the return of well production to its initial level.
The real-time data measured during the fishing operation favorably compared to the simulated forces predicted during job design and execution. The accuracy and reliability demonstrated by the CT simulation software in use enabled the operator to gain confidence in all simulations performed with the software for future CT operations.
This case study is the first known instance in which CT was used in conjunction with downhole tools that were supplied with continuous power to sensors to enable measurement of parameters, including force, pressure, temperature, torque, inclination, phasing, acceleration, gamma ray, and casing collar locator (CCL). This technology was supported by reliable software capable of simulating downhole conditions with precision and accuracy.