Acidizing Applications of Sandstones and Carbonates

This course is designed to provide training in the acidizing application for sandstones and carbonates of drilled wells as well as solutions to acid stimulation problems, health, safety and environment issues. Emphasis will be placed on the concepts of acid stimulation. Problems solving sessions are included to enhance learning objectives. Participants will need their calculators.

Learning Objectives

After completing this course, participants will be able to:

• Understand the near wellbore damage, its diagnosis, and stimulation.
• Apply the theory of acid-rock interaction (sandstone and carbonates) to the removal of damage and further stimulation. 
• Understand the benefits of matrix acidizing and acid fracturing.  

Learning Outcomes

• Understand fundamentals of acid stimulation of carbonates and sandstones.
• Design successful acid stimulation jobs.
• Perform pre- and post-acidizing analysis and acidizing cost analysis.

• Well completion engineers
• Production engineers
• Reservoir engineers
• Production geologists
• (Graduate and Junior Engineers/Geologists with 0-5 years experience)

Day 1

Introduction – Fundamentals of Acid Stimulation and Applications

• Acid-Rock Interaction – Basic Mechanism
• Formation Damage – Characterization, Origin, Diagnosis, & Treatment Strategy
• Stimulation Technique Determination
• Types of Acids and Acid Additives
• Types of Acidizing Treatments - Matrix Acidizing & Acid-Fracturing
• Stoichiometry Reactions (Gravimetric and Volumetric Dissolving Powers Concepts)
• Acid-Mineral Reaction Kinetics

Day 2

Practical Oilfield Considerations Concerning Acidizing

• Acid Job Quality
• Potential Safety Hazards in Acidizing
• Acidizing Techniques in Carbonates: Wellbore Cleanout; Matrix Acidizing Carbonate Formations
• Mechanical Factors in HF Treatment- HF Volume Determination
• Additives for Sandstone Acidizing
• Well Preparation Prior to Acidizing
• Treatment Stages for Oil Wells: Pre-Flush, HF-HCl, and Post-Flush Stages
• The Role of Mutual Solvents in Sandstone Acidizing
• Matrix Stimulation Treatment Evaluation
• Post- Treatment Evaluation – Return Fluid Analysis and Tracer Survey; Horner’s Method
• Economic Evaluation of Acid Stimulation

Day 3

Carbonate Acidizing

• Rock and Damage Characteristics in Carbonate Formation
• Distinctive Features
• Wormholes - Initiation and Propagation
• Carbonate Acidizing With Hydrochloric Acid
• Other Formulations (Other Acids)
• Carbonate Acidizing Design which involves the following:
  • Selection of acid type & concentration
  • Selection of type & amount of additives
  • Volume of main acid mixture
  • Injection rate of main acid
  • Placement of acid
  • Execution of treatment
  • Monitoring of treatment
• Candidate Selection, Pumping Schedule
• Additives, Placement Techniques
• Special Treatment for Carbonate Acidization
• Problem Solving Session

Day 4

Sandstone Acidizing

• Acid Selection
• Sandstone Acidizing Models
• Design process is as follows:
  • Identify that cause of poor well performance is damage
  • Establish that damage is removable by acidizing
  • Estimate formation fracturing pressure
  • Calculate a safe injection rate
  • Evaluate possible fluid stages
  • Select type and acid concentration
  • Calculate volume of each fluid stage
  • Calculate injection rates for optimum performance
  • Establish criteria for evaluation of the job
• Acidization of Horizontal Wells
• Problem solving session

Day 5

Acid-fracturing

• Acid Fracturing Objectives
• Fracture Direction, Length, Conductivity and Equivalent Skin Effect
• Modeling of Fracture Geometry
• Net Fracturing Pressure, Height Migration, and Fracture Toughness
• Acid Penetration in Fractures
• Acid Fracture Conductivity and Dimensionless Fracture Conductivity
• Productivity of an Acid Fractured Well
• Acid Fracture Design – An Integrated Model
• Problem Solving Session