Real Time Diagnostics of Gas Entries and Remedial Shut-off in Barefoot Horizontal Wells
Authors: Al-Behair Abdullah Mohmmed , Zeybek Murat , Malik Shauket , Lyngra Stig , Al-Hajari A. 
Published: February 2016

Abstract
Accurate diagnostics of wellbore fluid entry is crucial for the understanding of well performance, paramount for reservoir characterization purposes as well as the key element for identifying remedial action for isolation of unwanted fluid entry. Although multiphase production logging can be challenging in horizontal wells, especially in open hole barefoot completions, advances in production logging technology provides more confident results to allow design of shut-off remedial actions that can significantly improve future well performance.
In this paper, two well examples are presented showing real time diagnostic of gas entry intervals by advanced production logging in two similar barefoot-completed horizontal producers. Both wells were production logged due to an abnormally high producing gas-oil ratio with the objective of identifying remedial action. In both wells, a new compact advanced technology production logging tool was utilized. This new tool has been designed to provide more confident real time results in multiphase horizontal flow conditions.
The first well example demonstrates the presence of a major gas entry interval close to the heel section of the well with an additional less significant gas entry interval close to the middle of the horizontal section. A subsequent remedial workover was performed installing a passive inflow control device completion with two blank pipe sections across the gas entry intervals. The remedial result was a significant reduction in producing gas-oil ratio. Subsequently, a second diagnostic log was run to evaluate the post remedial action flow profile.
The second well example shows identification of a distinct gas entry from a short interval strongly suggesting that gas is coming through a high permeability fractured or vuggy geological feature penetrated by a horizontal barefoot well. In the near future, a remedial workover to install a passive inflow control device completion, including a blank pipe section across the gas entry zone, will be executed.
The results shown in this paper provide well examples of gas-oil horizontal production logging operations and interpretation, including effective shut-off. These results showed that it is possible to achieve challenging objectives and improve productivities due to advances in modern production logging and completion technology.

Introduction
Integrated production logging is required to obtain accurate flow profile, well performance, and effective well length as well as for obtaining accurate diagnostics of unwanted fluids to plan remedial action. Segregated multiphase flow regimes exist in horizontal wells where small deviation changes due to undulations can cause significant holdup and velocity variations along the wellbore. In addition, the presence of sumps and debris can disturb the sensor response. Hence, horizontal well flow regimes should be well understood; and the tool string should be designed to provide continuous velocity and holdup measurements. Oil-water flow regimes1 and gas-liquid (Fig. 1) flow regimes2 have been studied and shown that it could be challenging for velocity and holdup measurements.
The first integrated production logging tool was developed to overcome these measurement challenges3 was made available in the market place some 10 years ago. This early tool string was designed to provide confident results and some of the field examples4, 5 report excellent data quality. The tool string was long and depended on many stationary measurements in a horizontal well environment. It also lacked the ability to provide continuous gas velocity measurements. Reference 6 presents a field case of a high gas oil ratio (GOR) open hole horizontal well; however, no remedial action or post shut-off data was included. Another field example of high GOR is given in perforated cased holes7 with limited remedial work results. One more field example of high GOR horizontal well including assessment of remedial work through reservoir simulation is provided in Reference 8.
A new compact production logging tool was developed later and provided three-phase continuous measurements with real time answers9–11.