Well Pad

The Western Operating Area of the Prodhoe Bay field in Alaska gathers oil and gas front 17 remote well pad facilities, covering an area of 108 square wiles. Three Gathering Centers, each capable of handling 300 HB/D of oil and 480 MMSCF/D of gas, preprocess the oil before shipment via the Trans-Alaska pipeline. 

The Western Operating Area (WOA) contains three oil Gathering CenterE (DCs) each capable of processing 300,000 BPD <2000m3/h) oil and 480 MMSCFD (S86,OOOm3/h) gas. There are 17 remote well pads connected to the GCs by the surface flowlines. The wells are directionally drilled from the well pads there may be up to 30 wells per well pad. Figure 1 shows the relative locations of the surface facilities. 

A point was reached in the development of the field when a flowline dedicated to each well, although operationally convenient, wa no longer economically justified. A system of well pad Manifolding was devised to MasiMixe the exiating flowline capacity. It also became apparent that additional teat separation equipment would be required to acco—sedate the increased number of wells and more frequent testing requirements necessary dus to tha increase in problem walls. For economic reasons the additional separation equip-nent la more effectively located at the well pads. 

The testing procedure tor well pad test separators is essentially the sane as with GC test separators. The HOC operator aelects the well to be tested and interlocked logic operates the well pad diverter valves to divert the well Into the test vessel. 

Oil, gas and watar flow rates and veasel temperature and presaura together with choke sise and upstream cboke pressure at the well pad are monitored by the computer as before. At the end of the test, reports are produced and three point test data In the well file is updated. Because only a single stage separation process at elevated pressure is used, PVT data stored in the computer is used to correct the measured fluid voliones to standard conditions. Production allocation is handled in the same way by using the upstream choke pressure correlation. 

After consideration of all the technical and economic aspects of expanding the existing system versus installing a completely new system, the Honeywell system was replaced by a TRK system of ouch greater speed and capacity (see Figure S). Also added waa a SCADA console at each GC control roam to allow the CC operators to monitor well pad operationa and if necessary to take control action. Another addition was a revised microwave communications network thet includes the well peds. The system has an inner dual redundant loop for the most critical communications path between GCs, HOC, and CPS, with redundant radial shots from each GC to its associated well pads. 

The GC consoles consist of two color CRTs, keyboard and one printer. In addition to RTUs at the gcs, each well pad has an RTU. Communications between each RTU and the HOC are via either of two separate switchable channels. The coatputer monitors the error rates on the operating channel and will automatically switch to the standby channel, should this exceed acceptable levels. 

An important feature of the distributed control system chosen is that the PCMs can communicate over a microwave link, thus allowing the well pad manifold modules to be included in the GC control system the hardwire data highway is limited to a distance of 5000 ft. (1524m) from the Host. The well chokes and manifold controls will remain on the SCAOA system, but the well pad will require continuous process control of the test separator, water injection flow control, and artificial lift gas flow control. 

Significant economic advantages are realized in terms of operating cost when the alternative of manned remote well pad facilities are compared to remote control. 

Directional drilling—The technique of drilling at an angle from a surface location to reach a target formation not located directly underneath the well pad. 

The well pad provides a ground seal around the casing. The pad is constructed of reinforced concrete 6 x 6 ft (6 inches thick) with the well head located in the middle. The well pad prevents contaminants from collecting around the well and seeping down into the ground along the casing. 

Access Roads, Well Pads, and Mineral Rights... 

It is too early in shale gas drilling and production process history to determine the final well spacing that will most efficiently recover the gas resource in all basins however, current experience indicates that the use of horizontal well technology will significantly decrease the total environmental disturbance. As a case in point, consider that complete development of a 1-square mile section could require 16 vertical wells, each located on a separate well pad. Alternatively, six to eight horizontal wells (potentially more), drilled from only... 

A. It is EPA s intent that the 10 barrels per day of oil throughput referenced in 98.233(j) be based on annual average daily throughput. On an annual basis, the owner/operator must evaluate whether individual well pad produced hydrocarbon liquids falls above or below the equipment threshold and use monitoring methods appropriately. For less than 10 barrels per day of oil throughput on an annual average daily basis, the reporter must determine if 98.233(j)(5) applies. 

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