Improved Production Log Interpretation in Horizontal Wells Using a Combination of Pulsed Neutron Logs, Quantitative Temperature Log Analysis, Time Lapse LWD Resistivity Logs and Borehole Gravity

Abstract

Abstract A novel combination of logs and their unique interpretations are used to improve the understanding of production in horizontal wells on the North Slope of Alaska. Two techniques using Pulse Neutron Capture (PNC) logs to identify and quantify liquid productive intervals were previously presented in a paper by Brady et. al1. These techniques are compared and combined with two additional techniques: 1) the use of time lapse LWD resistivity to determine productive intervals and liquid flow profiles while drilling, and 2) a non trial-and-error method to determine quantitative gas production using temperature logs in a two-phase flow. Finally, modeling shows borehole gravity logs can be used to track the vertical movement of gas or water tens of feet above or below horizontal wells. Integrating the time lapse differences between shallow LWD resistivity logs run while drilling and logs run several hours after drilling show a strong correlation with PNC liquid flow profiles for wells producing at solution GOR. Additionally, combining a quantitative gas flow rate analysis from the temperature log with the liquid profile provides a complete analysis of the production profile for two-phase flow in horizontal wells. Finally by combining the production profile analysis from a horizontal well with the modeled timelapse borehole gravity data, a complete understanding of the fluid movements in the well borehole and up to two hundred feet into the formation can be obtained. These techniques can be applied to both horizontal and vertical wells with both slotted liner and cemented perforated completions to obtain a quantitative production profile. The LWD resistivity data, collected while drilling, provides an indication of the productive reservoir rock before the well is completed. Time lapse borehole gravity provides an understanding of the reservoir fluid movements affecting the wellbore flow profiles after the well has been put on production.