The site may have been selected because of wells drilled some distance from the proposed location but on a terrain that appeared similar to the proposed site. Wildcats are drilled where little or no known geological information is available. ![]() Infill wells and re-entries require minimum planning in most cases. Generally, wildcats require more planning than the other types. The drilling engineer is required to plan a variety of well types, including: wildcats, exploratory holes, step-outs, infills, and re-entries. This requirement of the well planning process can be difficult to achieve in abnormal-pressure, deep zones that can cause hole-geometry or mud problems. The hole or producing formation is not irreparably damaged.The hole diameter is sufficiently large so an adequate completion can be made.In this case, the term "usable" implies the following: Drilling a hole to the target depth is unsatisfactory if the final well configuration is not usable. 11.1-Well costs can be reduced dramatically if proper well planning is implemented. On the other hand, funds should be spent as necessary to develop a safe system.įig. It is not noble to build "steel monuments" in the name of safety if the additional expense is not required. In most cases, costs can be reduced to a certain level as additional effort is given to the planning ( Fig. A valid objective of the well-planning process is to minimize the cost of the well without jeopardizing the safety aspects. $800 to $1,000 to obtain proper drilling data. The incident probably would not have occurred if the contractor had spent U.S. The final settlement by the insurance company was more than U.S.The drilling contractor did not research the surrounding wells thoroughly in an effort to detect problems that could endanger his well or crews.All problems appeared to occur after a 1973 blowout taken from a 12,200-ft abnormal-pressure zone.A total of 16 of the remaining 48 wells had taken kicks or severe gas cutting from the same zone.It appeared that the blowouts came from the same zone as the well in question. However, 4 of the 52 wells in the specific township and range had blown out in the past five years.All wells in the area appeared to be normal pressured until 9,800 ft.The rig was destroyed and natural resources were lost until the well was killed three weeks later.Ī study was conducted that yielded the following results: An underground blowout occurred that soon erupted into a surface blowout. At that point, responsibility would be turned over to the oil company.ĭrilling was uneventful until a depth of 8,750 ft was reached. casing to 1,800 ft and use a 9.5-lbm/gal mud to 9,000 ft in a 9⅞-in. Because the prospect well was to be drilled to 9,000 ft, pressure problems were not anticipated. Although the records were approximately 15 years old, it appeared that the formation pressures would be normal to a depth of 9,800 ft. The drilling superintendent called a bit company and obtained records on two wells in the section where the prospect well was to be drilled. The contractor was reputable and had a successful history. ![]() ![]() The well was in a high-activity area where 52 wells had been drilled previously in a township (approximately 36 sq miles). ![]() Example 11.1 illustrates a case in which this consideration was neglected in the earliest phase of well planning, which is data collection.Įxample 11.1 A turnkey drilling contractor began drilling a 9,000-ft well in September 1979. This design requirement must be adhered to rigorously in all aspects of the plan. The well plan must be designed to minimize the risk of blowouts and other factors that could create problems. The second priority involves the safety of the well. Failure to stress crew safety has resulted in loss of life and burned or permanently crippled individuals. In some cases, the plan must be altered during the course of drilling the well when unforeseen drilling problems endanger the crew. Personnel considerations must be placed above all other aspects of the plan. Safety should be the highest priority in well planning. Unfortunately, it is not always possible to accomplish these objectives on each well because of constraints based on geology, drilling equipment, temperature, casing limitations, hole sizing, or budget. The objective of well planning is to formulate from many variables a program for drilling a well that has the following characteristics: safe, minimum cost, and usable. 5 Preparation of Authority for Expenditures(AFE).
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