Analysis of Onshore Vertical Well Well Name: Tim Tom

Well Summary:- Onshore vertical Well- Area = 40 Acres- Hole Diameter 8-7/8 in.

Inflow Parameters

Static reservoir pressure: 4,000 psi

Static reservoir temperature: 150 F

K = 50 md

H = 30 ft.

A = 40 acres (well is in the center of a circle or square)

Hole diameter = 8-7/8 in.

Initial Skin = 10

Water cut = 50%

PVT Data

Solution GOR = 500 scf/stbOil gravity = 30 API

Gas gravity = 0.7

N2 = 0.5 mole %

CO2 = 1 mole %

No H2S.

Water salinity = 50,000 ppm

Outflow Data

Surface system pressure = 120 psi (disable further surface system influences)

Flowing surface temperature = 110F.

2-7/8” 6.5# tubing to 9500 ft.

5-1/2” 17# casing to TD.

Mid-point of perforated interval at 9950 ft.

Use default roughness (0.0006 in.)

Production History:

Cumulative Oil Production (mstb)

Oil Cut (fraction)

200 1

220 .9

242 .8

266 .7

293 .6

322 .5

Current Well ConditionAt current conditions, the well has the potential to produce 1035.7 STB/day

at absolute open flow (AOF). Surface system pressure is at 120 psi, and we are producing from 2-7/8” tubing down to 9500ft. 5-1/2” casing is ran to TD. This well currently has a skin of 10, and we believe that this is seriously hindering the production potential of the well. There is also a significant water cut of 50%. This means that for every STB of oil we produce, we are also producing a STB of brine. Our team can substantially increase production potential of the well by reducing skin, creating gas lift, or some combination of the both.

The first and most drastic solution to increasing the production of the well will be to decrease skin to as close to zero as possible. An alternative method of increasing production would be to install a gas lift system. First, we will focus on decreasing skin, because it provides the largest increase in net gain.

Below is a representation of how the well will react to a reduction in skin by half, and then completely. This chart simply shows what the potential flow rate of the well with a skin of 10, 5, and 0. The line to the far left is with a skin of ten. The middle is a skin of 5, and the line showing the greatest production rate is with a skin of 0. As you can see a skin of 0 would substantially increase the fluid production of

our well. This shows the liquid flow rate but taking into account the 50% water cut, the oil rate is given below.

Skin AOF (liquid)(stb/d)

AOF (oil)(stb/d)

0 2713 1356.55 1450 725

10 1036 518

One option to reduce the skin is to have an acid job done to the hole. The price range is dependent upon the chemical you use for the job, but with oil at 45 dollars a barrel in today’s market, an acid job reducing your skin by 50% will increase revenue from this hole by approximately $9000 per day. If you were to remove the skin completely you could increase revenue up to approximately $36000 per day. These revenues do not account for the royalty negotiated with the landowner and the cost of extraction. Including a royalty of 12.5% for the oil and gas, the revenue would then be reduced to an amount of $31,500 per day, for the maximum reduced skin, before extraction cost is included. If we could efficiently acidize the well for less than $100,000, the net capital from this process will far outweigh the initial cost.

This, however, is absolute open flow rate of the well. Although AOF is useful to compare flow potential of a well, it is not actually a feasible production rate of the well. With the parameters Tim Tom has on the surface, we found the natural flow rate of the well to be an additional piece of useful information to use comparatively. We can observe the IPR vs. VLP plots to obtain the rate at which this well will flow under its own power with no additional recovery methods. This graph also has a 50% water cut so the oil flow rate is given in the chart.

Skin Natural liquid flow (stb/d)

Natural Oil Flow (stb/d)

10 315 157.55 500 2500 900 450

If the skin is left at 10, the natural flow rate of the well will be at 300 bbl/day. This can be increased by reducing the skin. As previously shown, the skin reduction drastically improves well flow. At a skin of 5, flow is increased to 500 bbl/day. Also, by removing the skin completely we see a flow of 900 bbl/day. With oil at $45 a barrel, you’re looking at gaining an extra $13500 per day with this hole.

As pressure declines in the well, there will be an increase in water encroachment. At a water oil ratio of 1.4 you will see the well with a skin of 10 stop flowing naturally because there is too much water in the hole. Looking at the wells with lower skin values, we see a greater resistance to WOR. The well with a skin of 5 can flow up to a 1.7 WOR and the well with no skin can flow naturally up to a WOR of 2.4. At this point in time, another method will be needed to continue production.

Looking at the production history, we can determine how many barrels will be produced as this well reaches the water cut at which it no longer flows.

Skin WOR where flow stops

Oil cut Oil produced(mstb)

10 1.4 40% 4005 1.7 38% 4000 2.4 42% 400

By seeing that production will be the same at any of the given skins at their WOR, the only other option would be to add a gas lift to the reservoir to increase oil production.

Considering gas lift as an option, we may now observe how this will improve the well. With the 3 different skin options, we have forecasted what our flow will be if we inject gas at a rate of 100 mscf/day. In this projection we will be using single 3/16 in. orifice at 4000 ft. As it can be seen on the following graph, with gas injection, all the wells will flow at the WOR that previously had prevented flow.

As the well is produced, the WOR will continue to grow. Therefore, we’ve shown that if the WOR reaches 100, the well will still flow whether or not the skins are present. This is due to the gas injection from the previous charts. Therefore it would be in the wells best interest to have a gas injection orifice installed before the GOR reaches 1.3. However, if the well has its skin removed completely, it can flow naturally up until the WOR reaches 2.4. This gives the well a greater production rate than if the skin is present in the well.

After the Gas injection has been put into place, we can go back and determine how much of the oil can be produced, as well as, after the WOR has reached 100.

Skin Oil cut Oil produced once WOR is 100 (mstb)

10 .01 10505 .01 10500 .01 1050

In conclusion, after viewing the following representations of the well, you can see that removing the skin will only affect how fast the well will flow. At all 3 skins we can see the same amount of oil is produced, but not in the same amount of time. After the analysis of well Tim Tom, we believe that it is beneficial to produce from this well under the right circumstances and adjustments, at the price of oil in today’s market.