Abstract

Good engineering design and execution of gravel pack procedures can and have increased the oil flow pack procedures can and have increased the oil flow rates of wells in the Gulf of Mexico by many thousands of barrels per day. However, many completions have failed to perform at design rates. The primary reason is that design methods have neglected the effect of the damaged formation around perforations. If damaged perforations are considered along with the effects of perforation washing, well flow analysis can better predict expected well productivity and help select better completion procedures.

Introduction

An engineer's job is to increase productivity, decrease unit capital and operating costs and increase the profitability of a process or operation. Well Flow Analysis (WFA) is a dramatic example of what good engineering can do. WFA is the calculation and plotting of reservoir, sandface, bottom hole tubing, and wellhead pressures over a range of flow rates. WFA is described in Appendix C.

As an example of the benefits of good gravel pack design and execution, Conoco's Lafayette pack design and execution, Conoco's Lafayette engineering staff recently finished the completion work on a Gulf of Mexico platform. Using Well Flow Analysis, good filtering and well executed gravel pack procedures, a combined flow rate of about 11,000 procedures, a combined flow rate of about 11,000 BOPD was achieved. This compares to a peak production rate of about 5000 BOPD from an offset platform production rate of about 5000 BOPD from an offset platform with similar formations and a similar number of completions. Good design and execution of gravel packing procedures increased the production rate by about packing procedures increased the production rate by about 6000 BOPD on just one platform.

The production rate capacity of wells in the Gulf of Mexico can be inferred from the U. S. Department of the Interior periodic publication entitled "Approved Maximum Efficient Rates for Reservoirs and Approved Maximum Production Rates for Well Completions April 1, 1980.", etc. The Approved Maximum Production Rate (MPR) allowed in this publication is usually 110% of the actual production rate publication is usually 110% of the actual production rate achieved on a recent test of the specified well.

Table 1 shows that the highest production rate well in the Gulf of Mexico, in April 1980, had an approved MPR of 2813 BOPD, equivalent to an actual test production rate of 2557 BOPD. In April 1980 there were 4 wells in the Gulf of Mexico with indicated test rates Of more than 2000 BOPD, versus 13 such wells in April 1982. Table 2 shows that there were 3 wells in the Gulf of Mexico with an indicated test rate of more than 40 MMSCFPD in April 1980. The largest gas well in 1982 had a test rate of only 39.5 MMSCFPD. This may reflect the curtailment of purchases by the gas pipeline companies. Since 1979 purchases by the gas pipeline companies. Since 1979 Joe Mach, Kermit Brown and associates have been preaching the benefits of an engineering analysis preaching the benefits of an engineering analysis of a flowing well system, which they called Nodal Analysis. Their work contributed to the higher production rates. production rates. Conoco has assembled a set of computer programs which will calculate and plot the pressures at the sandface, bottom hole tubing, and wellhead at various rates. This plot, called a Well Flow Analysis Chart, is a powerful engineering tool to increase production rates per completion and for production rates per completion and for stewardship of the completion. Since April 1980 Conoco has tested some wells at flow rates above 2000 BOPD. Other operators have also reported high rate completions. Spies, Himmatramka, Smith and Thomas reported wells in the High Island Block A-537 Field which tested at 2700, 2318, and 4795 BOPD. Crouch and Pack reported 4 completions which averaged 36.5 MMCFPD.

These results plus the 6000 BOPD increase from one platform, mentioned in the introduction, indicate that the industry is achieving higher production rates. But many completions fail to perform production rates. But many completions fail to perform up to design. Some of the reasons are discussed below.

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