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Acid stimulation and fracturing in multiple layers formation requires an integrated approach to design and execute an effective stimulation treatment. An extensive campaign of acid stimulation on carbonate formation to increase productivity index in a deep High Pressure High Temperature (HPHT) gas bearing carbonate formation is discussed here. A high degree variation in permeability across long interval, stress barriers between target zones, and completion limitations were main challenges to design an effective stimulation treatment. The target was to achieve effective acid stimulation for multi-layers carbonate formation with different formation properties and stress barriers. Although all layers had similar initial pressures and gas compositions; but different properties. Comingled flow was planned from the formation, therefore effective stimulation for each layer was recommended to drain effectively and improve recovery. To assess the best stimulation strategy in early stage of development, complete set of diagnostics conducted across all formations before and after the acid treatment coupled with geomechanical studies on actual core samples. Various stimulation techniques were implemented from Small Matrix Treatments (SMT) with Coiled Tubing, Matrix Acidizing Treatments (MAT), High Rate Matrix Acidizing (HRMA), and Acid Fracturing Treatment (AFT). Thorough study of results as part of learning process was conducted to optimize the important parameters that affect the stimulation efficiency such as perforation strategy, completion design, diverter selection, fracturing design and implementation. The importance of modeling in optimization process, comparison between different treatment types and fluid systems is discussed supported by actual data such as temperature logs, post-treatment flowback analysis, pressure transient analysis and production logging results.

Drilling in high pressure high temperature (HPHT) deep gas reservoirs, with multiple shallow different pressure horizons, requires special techniques which include application of Managed Pressure Drilling (MPD), revising casing setting depths, improving casing strength, and refining mud design. This paper focuses on application of MPD in HPHT gas wells and also describes briefly other techniques which can improve drilling performance and reduce non-productive time.

A novel technique in acid stimulation to attain uniform and effective coverage described in this paper has been adopted to treat large multiple carbonate intervals simultaneously. This technique has been proven to improve efficiency, increase recovery, and sustain production rate. Zones Z1, Z2, and Z3 of gas bearing are targets to be produced comingled in a well. Z2 is capable to produce without stimulation while Z3 is a thick dolomite with perforation interval up to 100+ ft., and Z1 is relatively thin and exhibits tight dolomite lithology. Both matrix acidizing and acid fracturing were developed to treat Z3, but the main challenge was to overcome high permeability contrast in the long interval thereby equally stimulate the entire net pay interval. The acid stimulation method implemented has proven successful providing longer acid penetration, better etching, higher gas production, and better operating efficiency. Efficient diversion was a key for successful stimulation of Z3. The fiber-based particulate diverter has been utilized in bullhead stimulation treatments to improve zone coverage. The new diversion material comprises of a customized blend of degradable fibers and multimodal particles, designed to provide an effective isolation plug at the perforation as well as at face of the reservoir inside the fracture in a consistent manner, thereby allowing new zones to be stimulated and increase penetration distance. The diversion materials providing such temporary isolation degrades within hours after the treatment. This new diverter has been used for matrix acidizing in wells. Many conclusions can be made by analyzing the acidizing experience in this field. The new composite diverter improves the diversion process in spite of the smaller volume of diversion material used compared to treatments with only fiber-based diverter. Although the new particulate diverter was initially developed for acid fracturing applications, experience shows its excellent effectiveness in high-rate matrix acidizing treatments.

The upstream Field Development Plan (FDP) and project delivery requires gated approach, close team collaboration, and synergy among all disciplines for success. This paper discusses a thorough phase-gate process with five phases and four gates to develop gas fields. The five phases comprise of Scoping of Project, Building Business Case, Appraisal and Testing, Full Field Development, and Monitoring. Critical elements before embarking on a field development with limited available data, and initial data gathering requirements in successful field development are discussed in details. Added benefits from project management, open communication, synergy and quick data analysis and decision-making during planning and executing are also described.