### LOW PRESSURE WELL DEFINITION

BACKGROUND: Formation pore pressures are defined as normal or abnormal. Abnormal f ormation pressures (over

pressure or under

- pressure) are determined with respect to t he freshwater pressure gradient. If a reservoir rock is found at 2000 feet , the freshwater gradient or n ormal pressure , would be equivalent to 2000 feet x 0 .433 psi/ft = 866 psi. To put the term “freshwater gradient” into context and to define 0

. 433 psi/ft in layman terms, consider a swimming pool that is 10 feet deep

. T he pressure will increase as one goes deeper and be notice able by the pressure exerted on the inner ear. This pressure is due to the weight of water ( 8.33 lbs/gal) which is stacked on top of itself

- known as h ydrostatic pressure

.

 Freshwater Hydrostatic Gradient = 8.33 lb/gal X 0 .052 = 0. 433 psi/ft ( 0 .052 is a conversion factor that changes from units of lbs/gal to psi/ft )

 Freshwater Hydro static Pressure = 0

. 433 psi/ft X depth (ft)

 T o find Hydrostatic P ressure at the bottom of a 10 f oo t swimming pool: 0

. 433 psi/ft x 10 ft = 4.33 psi exerted on the inner ear In normally pressured formations , it is assumed that the rock matrix itself is supporting the entirety of the overburden forces. This support of the overburden by the matrix itself allows pore pressures to exist at no more than a typical hydrostatic column of fluid at a particular depth. When the rock matrix itself is not the sole support of the overburden , the pore fluids take on part of the load causing the fluids to be in an
over
- pressured environment. Other naturally occurring geological conditions can also contribute to a n over
pressured formation. Some of the reasons for formation pore pressure to be under

- pressured or “sub

- pressured” could be from:

 Fluids withdrawal (past production) indicating depletion ;

 Geological event where some degree of overburden erosion has taken plac e ; and

 Naturally occurring pore fluids migration has taken place

. For many years the o il and g as industry , along with other governmental bodies and professional organizations , have recognized the freshwater hydrostatic gradient

. D etermin ing the fresh water hydrostatic gradient and the pressure regime associated with the field is a simple mathematical equation and concept accepted by the industry and the Department of Energy

. It has also been used and accepted by industry and governmental ag encies to be the basis of well control and blow out calculations

. The f reshwater hydrostatic gradient pressure is considered to be the base line of normal pore pressure. A well whose reservoir(s) pressure is less that the freshwater hydrostatic gradient is defined as under

- pressure or low pressure. A well whose reservoir(s) pressure is greater that the freshwater hydrostatic gradient is defined as over

- pressure or high pressure. In basins throughout the country , e ngineers, geologist s, and stimulation companies have used the freshwater gradient and the resulting well head pressure not only to design artificial stimulation treatments, but to position casing strings to support environmentally sound drilling methods. (See referenced artic les attached). These formations , due to their under

- pressure d nature , must be drilled andcompleted in a fashion that is not detriment al to its productive capabilities (typically , the less fluid the

better).

A low or under

- pressure d reservoir in many in stances requires the use of inert gases to afford the operator the ability to economically produce natural gas. A well that is under

- pressure d will not have the energy to clean up , or flow

- back a column of water due to the lack of pore pressure. Thus , inert gases are often used to dramatically reduce the hydrostatic pressure during flow

- back operations. Inert gases bring on challenges to the small producer with the regulations and the ability to strip these gases to meet required pipeline qualit y . Ni trogen and CO 2 are commonly used inert gases. In high concentrations they will not flare. Pipeline standards are typically capped at 4% of total molecular content for inert gases

.
U nder

- p ressure d wells in most cases are economically marginal well s . Th e following characteristics are indicative of a low or under

- pressure well :

 Foot print is very small 1 to 3 acres

.
 Flow

- back times are less than three days , with much smaller amounts of hydrocarbons being produced.

 Stimulated with inert gases or a mixture of gas and water that use less than 5000 barrels of water (see West Virginia Department of Environmental Protection regulations)

.
 Total cost s are $400,000 to $1,000,000 compared to $7,000,000 to $12,000,000 for the large r unconventional wells with horizontal components

.
 Smaller producers are primarily found in the under

- pressure areas primarily because of the volumes each well produces. Prior to the new unconventional plays , these small producers were the backbone of the US natural gas indust ry
. Subpart OOOO states that any well meeting the definition of a low pressure gas well will be exem p t from green completion requirements utilizing REC

. This exemption is in place due to the inadequate bottom hole pressure to lift fluids to surface, move through surface equipment , and overcome pipeline pressures. The formula used by the Environmental Protection Agency to define a “ l ow pressure well” utilizes models and makes numerous assumptions and estimations to determine a usable standard to relate flu id velocities and pressure drops. The EPA’s development of the low pressure formula includes the following assumptions or values :

 Pressure decreases in reservoirs ;

 Pressure d ecreases along well tubulars ;

 Tubular diameters ;

 M ultiphase fluid densities ;

 Temperatures, gas molecular weights and compressibility ;

 Changing f low regimes ;

 Pressure d ecreases along REC equipment ; and

 Pressures at s ales an d or gas gathering system (which can be very dynamic)

. The EPA derivation and formula for calculating a “low pressure” well is overly complicated, rife with assumptions , and ultimately fails to capture what the industry has historically considered a low pressure well.As mentioned above, a critical difference between low pressure wells and other wells is the l ength of

flow

- back

– with a low pressure well flow

- back period being less than three days. In EPA’s cost

- effectiveness evaluation of RECs, it assumed an average of seven days

– over twice the length of the flow

- back for low pressure well s
. Additionally , the period of flow

- back where the flow is gas dominant is very short

– perhaps a number of hours. RECs on low pressure wells are simply not cost

- effective, and if required, would likely make a significant portion of the low pressure wells uneconomical. N o t only are the “benefits” over exaggerated for RECs on low pressure well s , but also the environmental “costs.” With the flow

- back period less than ha lf of what EPA assumed, the potential to emit VOCs is also less than half.

PROPOSED DEFINITION OF A "LO W PRESSURE WELL"

A low pressure well should be defined as: A well where the field pressure is less than 0.433 times the vertical depth of the deep est target reservoir and the flow

- back period will be less than three days in duration Example

o If a well that is 4500 feet T VD has a reservoir pressure of 1200 psi , the corresponding pressure gradient is 0.27 psi/ft, this g radient is less than the .433 psi/ft freshwater column , thus , indicating an under

- pressure reservoir , i.e. , a low pressure well

.