Formation Damage in Tight Gas Reservoirs

Abstract

The increased demand for more sources of clean energy such as natural gas from unconventional reservoirs has forced the industry to explore the more challenging tight gas reservoirs. Tight gas reservoirs constitute a significant proportion of the world's natural gas resource and offer great potential for future reserve growth and production. However, to meet future global energy demand, access to tight gas reservoirs requires innovative and cost effective technical solutions.Yet, tight gas reservoirs are often characterized by complex geological and petrophysical systems as well as heterogeneities at all scales. Exploring and developing tight gas accumulations are both technically and commercially challenging due to the large subsurface uncertainty and low expected ultimate recovery per well. In addition, formation damage is an undesirable operational and economic dilemma that may occur during any phase of gas recovery from tight gas reservoirs. Tight gas reservoirs normally show significant damage during well drilling, completion, stimulation and production. Therefore, they may not flow gas at optimum rates without advanced production improvement techniques.The main damage mechanisms and the factors that have significant influence on well productivity in tight gas reservoirs include mechanical damage to formation rock, plugging of natural fractures by mud solid particles invasion, relative permeability reduction around wellbore as a result of filtrate invasion, liquid leak-off into the formation during fracturing operations, water blocking, damage due to wellbore breakouts, compression damage and the damage associated with perforation. Drilling and fracturing fluids invasion mostly occur through natural fractures and may also lead to serious permeability reduction in the rock matrix that surrounds the natural or hydraulic fractures.Prevention, control and remediation of formation damage are among the most important issues to be resolved for efficient exploitation of tight gas reservoirs. Designing certain chemicals and/or treatment procedures for damage control and remediation is not an easy scientific and engineering task. Good understanding of the formation damage mechanisms would allow operators to make informed decision as to the best practices to drill, complete and produce tight gas wells.In this paper, a review of commonly practiced methods and tools available for prevention, control and remediation of formation damage will be discussed and presented.

Impact of Supercritical CO2 on Shale Reservoirs and Its Implication for CO2 Sequestration

“…74 In such a scenario, underbalanced drilling (UBD) is helpful because, in place of heavy drilling fluids and muds, a light mineral oil, 75 nitrogen foam, 76 and sometimes compressed air 77 are used to achieve underbalanced well conditions and the low density of such drilling fluids will cause the hydrostatic pressure in the wellbore to be lower than the internal fluid pressure of that formation, resulting in the production of reservoir fluids while drilling. 78 However, the density of these fluids is not sufficient enough to generate enough torque for the bottom-hole motors to rotate at its maximum efficiency. 79 Fortuitously, SC-CO 2 , because of its liquidlike density, is able to provide sufficient power to rotate the down-hole motor.…”

“…Traditionally, water-based fluids were used for drilling tight gas reservoirs for the recovery of oil and gas resources. , However, unconventional reservoirs vulnerable to formation damages are not ideal to drill with water-jets because it can cause excessive overbalance condition near the bottom hole, resulting from the hydrostatic pressure exerted by the produced mud . In such a scenario, underbalanced drilling (UBD) is helpful because, in place of heavy drilling fluids and muds, a light mineral oil, nitrogen foam, and sometimes compressed air are used to achieve underbalanced well conditions and the low density of such drilling fluids will cause the hydrostatic pressure in the wellbore to be lower than the internal fluid pressure of that formation, resulting in the production of reservoir fluids while drilling . However, the density of these fluids is not sufficient enough to generate enough torque for the bottom-hole motors to rotate at its maximum efficiency .…”

Experimental Investigation on the Penetrability Mechanism of Gel Slug During Well Completion Processes

“…The global demand for oil and natural gas resources is increasing daily, which brings a great challenge to the oil and natural gas companies due to the increasing difficulties of well drilling and completion, − especially for the exploration and development of low permeability of oil and gas fields. The development of low permeability reservoirs has become a major trend presently. − With the continuous improvement of exploration technology, the quality of the newly developed oil and gas reservoirs will become worse and worse, and the proportion of low permeability reserves will become higher and higher. − In low permeability reservoirs, the formation is very vulnerable to pollution and damage, and the production of oil and gas wells is low due to the tight cementation, muddy and fine minerals, low porosity, stress sensitivity, and low effective permeability. − Therefore, it is very important to protect reservoirs, reduce and avoid pollution for long-term development, and stable production of low permeability oil and gas fields. − …”

Study on Matrix Damage and Control Methods of Fracturing Fluid on Tight Sandstone Gas Reservoirs

“…The small size of these pores and throats increases the susceptibility of the reservoir to secondary damage caused by the fracturing fluids (FFs). Extensive research has demonstrated that physical and chemical damage are the primary types of damage in tight reservoirs, which can be attributed to various mechanisms including fluid sensitivity, intrusion by solid particles, phase trapping, sensitivity to stress, and adsorption of treatment agents. − …”