Drilling activity has radically increased in unconventional shale gas reservoirs. Non-aqueous based fluid (NAF) is frequently chosen as drilling fluids in these shale plays. While NAFs can bring benefits such as shale stabilization, lubricity, and contamination tolerance, environmental concerns and related costs are a problem. These difficulties let the operators to search for different fluid systems such as water-based muds (WBM).

Even though there is some operational alikeness, there exist a wide range of downhole conditions for shale plays such as shale mineralogy and bottom-hole temperature. Thus, a single water-based solution to aim shale plays generally is not a realistic option. Instead, a customized approach that formulates a water-based mud system for a specific shale play has been attended. Customization depend on some factors of a given shale play such as the shale morphology and lithology, drilling considerations, and other reservoir-specific variables.

In this study, two different WBMs investigated for Silurian Dadas shale formation found at south east Turkey. Full laboratory development, rheological and filtration testing are described. Additionally, the contamination and interaction of the drilling fluids systems with shale samples are examined. The experimental results shows proper rheological and filtration properties and these muds may be an alternate to NAFs with enhanced environmental and economic benefits. This study broadens our view and discusses the development of water based muds for other shale plays which have similar properties as Silurian Dadas Shale.

1. Introduction

Predictable gas reserves have been intensely raised in the last decade due to the influence from unconventional shale plays [1]. By the application of horizontal drilling and hydraulic fracturing techniques, these shale plays got an important role in evaluating oil reserves in recent decades [2]. Although unconventional gas reserves maintain resemblances in the way they are drilled and produced, in fact there are many vital modifications between plays. These modifications are physical dissimilarities such as the mineralogy of the formation, the bottomhole temperature (BHT) of the well, and petrophysical values (Young's modulus, Poisson's ratio etc.) [3].

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