Matrix acidizing stimulation in carbonate formations with open hole and multilateral completions presents several challenges to insure an optimum treatment is performed. Each lateral must be accessed to place and clean up the acid treatment. The key objective of the intervention is not only to eliminate as much as possible the damage in the matrix produced by the drilling and completion process, but also trying to connect to high conductive fractures that will maximize the drainage of hydrocarbons out of the formation. In this type of completions, traditional practices are limited to spot stages of fluids (pre-flush, acid, and diversion) in front of the formation without much control over the placement.
This document describes, through a field experience, how new Coiled Tubing (CT) conveyed downhole measurements can assist to overcome the challenges above, enabling more intelligent interventions. An innovative workflow designed to optimize stimulation treatments as they occur was implemented for the first time in Saudi Arabia on a sub-hydrostatic, trilateral horizontal openhole oil producer. The workflow uses as reference formation porosity or permeability logs as well as Distributed Temperature Surveys (DTS) for the evaluation of distribution and fluid temperature responses to decide selective placement of stimulation fluids. A consistent lateral fluid flow distribution from the preflush stages and acid stage treatments in each well's lateral, as well as a bullhead injection test recorded in the main bore, is presented. Selective lateral access was enabled by using an Indexing Flow-activated Bent Sub (IFBS) and confirmed upon entry using a real-time casing collar locator (CCL).
The well began producing at the maximum capacity of the ESP pump used to clean the well after the acid treatment, with results that exceeded expectations, effectively overcoming the high drawdown and low Productivity Index (PI) observed in the well.
This experience demonstrates that innovative downhole measurements in combination with the referred workflow make possible to understand fluid distribution and control fluid placement with Coiled Tubing, unlocking the well production potential. This new technique is proven to be an optimum solution for the type of completions commonly found in Middle East.