Abstract

Unconventional gas resources offer the only significant gas production growth potential in the coming years, currently accounting for 43% of the US gas production. Tight gas represents approximately 70% of the unconventional production and significant reserves are yet to be developed. In the United States, Utah, Colorado and Texas host the vast majority of those resources. Other major potential fields are located in China, Algeria, Argentina, Indonesia and the Middle East.

Drilling in mature depleted fields can be costly in non-productive time (NPT) associated with stuck pipe, whole mud losses and side tracks. A new water-based mud system addressing depleted tight gas reservoirs has been successfully introduced to provide increased drilling performance as compared to conventional water-based mud systems. The new High Performance Water Based Mud (HPWBM) is a viable solution for onshore drilling in mature, depleted tight gas sands. This technology is applicable to any tight depleted gas reservoir where losses or stuck pipe occur.

This paper provides a technical overview of the new HPWBM performance in a technically challenging field where massive losses, stuck pipe, twist-offs and other fluid associated NPT are common. The case histories presented are from an independent operator drilling in South Texas and highlight the successes and optimized learning curve of the system as compared to offsets drilled with conventional water-based mud (WBM) and oil-based mud (OBM) systems by the operator.

Introduction

With the increasing global demand for oil and gas, operators strive to maximize production. Operators are conducting more advanced drilling operations, such as extended reach, horizontal and high-pressure / high-temperature (HP-HT) drilling and are expanding globally into difficult and hard-to-reach locations. They are also drilling unconventional zones, such as those encountered in the Vicksburg formation in South Texas. Because of the technical difficulty associated with these wells and the remote areas in which they are drilled, exploration and development has become increasingly risky. Due to the technical benefits and ease of use associated with OBM systems, operators often overlook the use of WBM systems when drilling these types of wells. Although there are inherent advantages provided by OBM, they are often offset by strict regulations, costs for disposal, lost circulation events and concerns over the environmental impact associated with the system. Operators are constantly challenged to balance performance requirements with environmental, waste disposal, economic and logistical drivers.

Recently, a new HPWBM has been able to provide performance characteristics approaching that of OBM with reduced environmental impact. A potential deterrent to the use of HPWBM is the relative cost as compared to conventional WBM and OBM. However, if the HPWBM performs similar to an OBM, the benefits can justify the cost when considering the expense of disposal and lost circulation events commonly associated with OBM.

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