First Horizontal-Well Production Logging and Water Control Success in a Tough Completion Offshore Well: A Case Study from China

Abstract

The Wen Chang oil field in the South China Sea is exploited mainly with horizontal wells completed with a sand screen and equipped with an electrical submersible pump (ESP) plus Y-tool for the production string. The water cut in one well has reached 74%, making diagnosis of the water entrance critical for a success remedial operation in the well. Because flow regimes in highly deviated and horizontal wells are quite different from those in vertical wells, the velocity and holdup distribution are required for accurate flow rate and fluid entry determinations in multiphase flow. In addition to the sand screen completions and variation in the well trajectory, the presence of annulus flow makes the measurements even more complex. Production logging in horizontal wells can be challenging. An array of mini-spinners with optical gas and resistivity water holdup sensors was conveyed by an electrically powered tractor in the well along a 730-m horizontal interval. Two difficulties in conveying the tool string to TD were that the 5½-in. screen liner is directly hung inside 9 5/8-in. casing without entry guide and that the minimum restriction of the Y-tool bypass tubing is only 2.313 in, so the tool can easily be stuck inside the tubing. These difficulties were overcome by using a specially designed tool string. The operation was successful and high-quality logging data was acquired. Comprehensive interpretation shows that 74.7% of the water comes from the bottom 50-m interval. Recirculating water was also observed in the deviated interval. Based on the production log analysis and reservoir permeability distribution from logging-while-drilling data, a two-stage annulus chemical packer (ACP) was designed, with one stage to shut off the current bottom water entry and the other prepared for future water control. A production tubing string with flow control nozzles was installed after water shutoff to optimize fluid distribution along the interval. Water was successfully shut off in this horizontal well.

Evaluation of Liquid Production and Water Injection Profiles of Horizontal Well by Pressure-Transient Analysis: Field Cases

“…A semianalytical model is presented to estimate the locations of high-productive section based on the bottom-hole pressure data. 21,27 However, there are two issues not solved in the actual applications: (1) The effective producing length we obtained by current methods or softwares and our approaches 21,27 is less than the drilled or completed horizontal intervals. The misuses of the production rate distribution and horizontal well length would result in erroneous well and reservoir parameter interpretations.…”

“…Al Rbeawi and Tiab 20 introduced the mathematical models to study the effects of multiple zonal isolations on pressure responses and concluded that the dominant effect of isolators can only be identified during the early radial or linear regimes. Cheng et al 21 developed a well-test model for the horizontal wells with nonuniform production rate considering the segmented oil production and various skin factors in different production segments by Green's function and Newman's product tool. Nie et al 22,23 established a semianalytical model for horizontal wells in a homogeneous, dual, and triple-porosity reservoir and then developed a time-tracking test method to reduce the well testing costs.…”

Diagnosis of Water-Influx Locations of Horizontal Well Subject to Bottom-Water Drive through Well-Testing Analysis

“…Aibazarov et al [20] described how to determine the downhole fluid flow path and further to optimize water shut-off operations by using integrating data from spectral noise logging tools and multisensor production logging. Over the past few years, many researchers pinpointed water entry intervals through production logging [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. On the other hand, another monitoring system can provide vital data (e.g., pressure and temperature) for waterinflux detection.…”